assignment in an if statement

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Computer programming - JavaScript and the web

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• If Statements
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The if...else statement executes a statement if a specified condition is truthy . If the condition is falsy , another statement in the optional else clause will be executed.

An expression that is considered to be either truthy or falsy .

Statement that is executed if condition is truthy . Can be any statement, including further nested if statements. To execute multiple statements, use a block statement ( { /* ... */ } ) to group those statements. To execute no statements, use an empty statement.

Statement that is executed if condition is falsy and the else clause exists. Can be any statement, including block statements and further nested if statements.

Description

Multiple if...else statements can be nested to create an else if clause. Note that there is no elseif (in one word) keyword in JavaScript.

To see how this works, this is how it would look if the nesting were properly indented:

To execute multiple statements within a clause, use a block statement ( { /* ... */ } ) to group those statements.

Not using blocks may lead to confusing behavior, especially if the code is hand-formatted. For example:

This code looks innocent — however, executing checkValue(1, 3) will log "a is not 1". This is because in the case of dangling else , the else clause will be connected to the closest if clause. Therefore, the code above, with proper indentation, would look like:

In general, it is a good practice to always use block statements, especially in code involving nested if statements.

Do not confuse the primitive Boolean values true and false with truthiness or falsiness of the Boolean object. Any value that is not false , undefined , null , 0 , -0 , NaN , or the empty string ( "" ), and any object, including a Boolean object whose value is false , is considered truthy when used as the condition. For example:

Using if...else

Using else if.

Note that there is no elseif syntax in JavaScript. However, you can write it with a space between else and if :

Using an assignment as a condition

You should almost never have an if...else with an assignment like x = y as a condition:

Because unlike while loops, the condition is only evaluated once, so the assignment is only performed once. The code above is equivalent to:

Which is much clearer. However, in the rare case you find yourself wanting to do something like that, the while documentation has a Using an assignment as a condition section with our recommendations.

Specifications

Browser compatibility.

BCD tables only load in the browser with JavaScript enabled. Enable JavaScript to view data.

• Conditional (ternary) operator

Python Conditional Assignment

When you want to assign a value to a variable based on some condition, like if the condition is true then assign a value to the variable, else assign some other value to the variable, then you can use the conditional assignment operator.

In this tutorial, we will look at different ways to assign values to a variable based on some condition.

1. Using Ternary Operator

The ternary operator is very special operator in Python, it is used to assign a value to a variable based on some condition.

It goes like this:

Here, the value of variable will be value_if_true if the condition is true, else it will be value_if_false .

Let's see a code snippet to understand it better.

You can see we have conditionally assigned a value to variable c based on the condition a > b .

2. Using if-else statement

if-else statements are the core part of any programming language, they are used to execute a block of code based on some condition.

Using an if-else statement, we can assign a value to a variable based on the condition we provide.

Here is an example of replacing the above code snippet with the if-else statement.

3. Using Logical Short Circuit Evaluation

Logical short circuit evaluation is another way using which you can assign a value to a variable conditionally.

The format of logical short circuit evaluation is:

It looks similar to ternary operator, but it is not. Here the condition and value_if_true performs logical AND operation, if both are true then the value of variable will be value_if_true , or else it will be value_if_false .

Let's see an example:

But if we make condition True but value_if_true False (or 0 or None), then the value of variable will be value_if_false .

So, you can see that the value of c is 20 even though the condition a < b is True .

So, you should be careful while using logical short circuit evaluation.

While working with lists , we often need to check if a list is empty or not, and if it is empty then we need to assign some default value to it.

Let's see how we can do it using conditional assignment.

Here, we have assigned a default value to my_list if it is empty.

Assign a value to a variable conditionally based on the presence of an element in a list.

Now you know 3 different ways to assign a value to a variable conditionally. Any of these methods can be used to assign a value when there is a condition.

The cleanest and fastest way to conditional value assignment is the ternary operator .

if-else statement is recommended to use when you have to execute a block of code based on some condition.

Happy coding! 😊

cppreference.com

If statement.

Conditionally executes another statement.

Used where code needs to be executed based on a run-time or compile-time (since C++17) condition , or whether the if statement is evaluated in a manifestly constant-evaluated context (since C++23) .

[ edit ] Syntax

• expression which is contextually convertible to bool
• declaration of a single non-array variable with a brace-or-equals initializer .
• is evaluated in a manifestly constant-evaluated context , if ! is not preceding consteval
• is not evaluated in a manifestly constant-evaluated context, if ! is preceding consteval
• is not evaluated in a manifestly constant-evaluated context , if ! is not preceding consteval
• is evaluated in a manifestly constant-evaluated context, if ! is preceding consteval

[ edit ] Explanation

If the condition yields true after conversion to bool , statement-true is executed.

If the else part of the if statement is present and condition yields false after conversion to bool , statement-false is executed.

In the second form of if statement (the one including else), if statement-true is also an if statement then that inner if statement must contain an else part as well (in other words, in nested if-statements, the else is associated with the closest if that doesn't have an else).

except that names declared by the init-statement (if init-statement is a declaration) and names declared by condition (if condition is a declaration) are in the same scope, which is also the scope of both statement s.

both compound-statement and statement (if any) must be compound statements.

If statement is not a compound statement, it will still be treated as a part of the consteval if statement (and thus results in a compilation error):

If a consteval if statement is evaluated in a manifestly constant-evaluated context , compound-statement is executed. Otherwise, statement is executed if it is present.

A case or default label appearing within a consteval if statement shall be associated with a switch statement within the same if statement. A label declared in a substatement of a consteval if statement shall only be referred to by a statement in the same substatement.

If the statement begins with if !consteval , the compound-statement and statement (if any) must both be compound statements. Such statements are not considered consteval if statements, but are equivalent to consteval if statements:

• if ! consteval { /*stmt*/ } is equivalent to if consteval { } else { /*stmt*/ } .
• if ! consteval { /*stmt-1*/ } else { /*stmt-2*/ } is equivalent to if consteval { /*stmt-2*/ } else { /*stmt-1*/ } .

compound-statement in a consteval if statement (or statement in the negative form) is in an immediate function context , in which a call to an immediate function needs not to be a constant expression.

[ edit ] Notes

If statement-true or statement-false is not a compound statement, it is treated as if it were:

is the same as

The scope of the name introduced by condition , if it is a declaration, is the combined scope of both statements' bodies:

If statement-true is entered by goto or longjmp , condition is not evaluated and statement-false is not executed.

[ edit ] Keywords

if , else , constexpr , consteval

[ edit ] Defect reports

The following behavior-changing defect reports were applied retroactively to previously published C++ standards.

[ edit ] See also

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In computer programming, we use the if...else statement to run one block of code under certain conditions and another block of code under different conditions.

For example, assigning grades (A, B, C) based on marks obtained by a student.

• if the percentage is above 90 , assign grade A
• if the percentage is above 75 , assign grade B
• if the percentage is above 65 , assign grade C
• C++ if Statement

The if statement evaluates the condition inside the parentheses ( ) .

• If the condition evaluates to true , the code inside the body of if is executed.
• If the condition evaluates to false , the code inside the body of if is skipped.

Note: The code inside { } is the body of the if statement.

Example 1: C++ if Statement

When the user enters 5 , the condition number > 0 is evaluated to true and the statement inside the body of if is executed.

When the user enters -5 , the condition number > 0 is evaluated to false and the statement inside the body of if is not executed.

• C++ if...else

The if statement can have an optional else clause.

The if..else statement evaluates the condition inside the parenthesis.

If the condition evaluates true ,

• the code inside the body of if is executed
• the code inside the body of else is skipped from execution

If the condition evaluates false ,

• the code inside the body of else is executed
• the code inside the body of if is skipped from execution

Example 2: C++ if...else Statement

In the above program, we have the condition number >= 0 . If we enter the number greater or equal to 0 , then the condition evaluates true .

Here, we enter 4 . So, the condition is true . Hence, the statement inside the body of if is executed.

Here, we enter -4 . So, the condition is false . Hence, the statement inside the body of else is executed.

• C++ if...else...else if statement

The if...else statement is used to execute a block of code among two alternatives. However, if we need to make a choice between more than two alternatives, we use the if...else if...else statement.

• If condition1 evaluates to true , the code block 1 is executed.
• If condition1 evaluates to false , then condition2 is evaluated.
• If condition2 is true , the code block 2 is executed.
• If condition2 is false , the code block 3 is executed.

Note: There can be more than one else if statement but only one if and else statements.

Example 3: C++ if...else...else if

In this program, we take a number from the user. We then use the if...else if...else ladder to check whether the number is positive, negative, or zero.

If the number is greater than 0 , the code inside the if block is executed. If the number is less than 0 , the code inside the else if block is executed. Otherwise, the code inside the else block is executed.

• C++ Nested if...else

Sometimes, we need to use an if statement inside another if statement. This is known as nested if statement.

Think of it as multiple layers of if statements. There is a first, outer if statement, and inside it is another, inner if statement.

• We can add else and else if statements to the inner if statement as required.
• The inner if statement can also be inserted inside the outer else or else if statements (if they exist).
• We can nest multiple layers of if statements.

Example 4: C++ Nested if

In the above example,

• We take an integer as an input from the user and store it in the variable num .
• If true , then the inner if...else statement is executed.
• If false , the code inside the outer else condition is executed, which prints "The number is 0 and it is neither positive nor negative."
• If true , then we print a statement saying that the number is positive.
• If false , we print that the number is negative.

Note: As you can see, nested if...else makes your logic complicated. If possible, you should always try to avoid nested if...else .

Body of if...else With Only One Statement

If the body of if...else has only one statement, you can omit { } in the program. For example, you can replace

The output of both programs will be the same.

Note: Although it's not necessary to use { } if the body of if...else has only one statement, using { } makes your code more readable.

• More on Decision Making

The ternary operator is a concise, inline method used to execute one of two expressions based on a condition. To learn more, visit C++ Ternary Operator .

If we need to make a choice between more than one alternatives based on a given test condition, the switch statement can be used. To learn more, visit C++ switch .

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Table of Contents

• Introduction

Sorry about that.

Conditional branching: if, '?'

Sometimes, we need to perform different actions based on different conditions.

To do that, we can use the if statement and the conditional operator ? , that’s also called a “question mark” operator.

The “if” statement

The if(...) statement evaluates a condition in parentheses and, if the result is true , executes a block of code.

For example:

In the example above, the condition is a simple equality check ( year == 2015 ), but it can be much more complex.

If we want to execute more than one statement, we have to wrap our code block inside curly braces:

We recommend wrapping your code block with curly braces {} every time you use an if statement, even if there is only one statement to execute. Doing so improves readability.

Boolean conversion

The if (…) statement evaluates the expression in its parentheses and converts the result to a boolean.

Let’s recall the conversion rules from the chapter Type Conversions :

• A number 0 , an empty string "" , null , undefined , and NaN all become false . Because of that they are called “falsy” values.
• Other values become true , so they are called “truthy”.

So, the code under this condition would never execute:

…and inside this condition – it always will:

We can also pass a pre-evaluated boolean value to if , like this:

The “else” clause

The if statement may contain an optional else block. It executes when the condition is falsy.

Several conditions: “else if”

Sometimes, we’d like to test several variants of a condition. The else if clause lets us do that.

In the code above, JavaScript first checks year < 2015 . If that is falsy, it goes to the next condition year > 2015 . If that is also falsy, it shows the last alert .

There can be more else if blocks. The final else is optional.

Conditional operator ‘?’

Sometimes, we need to assign a variable depending on a condition.

For instance:

The so-called “conditional” or “question mark” operator lets us do that in a shorter and simpler way.

The operator is represented by a question mark ? . Sometimes it’s called “ternary”, because the operator has three operands. It is actually the one and only operator in JavaScript which has that many.

The syntax is:

The condition is evaluated: if it’s truthy then value1 is returned, otherwise – value2 .

Technically, we can omit the parentheses around age > 18 . The question mark operator has a low precedence, so it executes after the comparison > .

This example will do the same thing as the previous one:

But parentheses make the code more readable, so we recommend using them.

In the example above, you can avoid using the question mark operator because the comparison itself returns true/false :

Multiple ‘?’

A sequence of question mark operators ? can return a value that depends on more than one condition.

It may be difficult at first to grasp what’s going on. But after a closer look, we can see that it’s just an ordinary sequence of tests:

• The first question mark checks whether age < 3 .
• If true – it returns 'Hi, baby!' . Otherwise, it continues to the expression after the colon “:”, checking age < 18 .
• If that’s true – it returns 'Hello!' . Otherwise, it continues to the expression after the next colon “:”, checking age < 100 .
• If that’s true – it returns 'Greetings!' . Otherwise, it continues to the expression after the last colon “:”, returning 'What an unusual age!' .

Here’s how this looks using if..else :

Non-traditional use of ‘?’

Sometimes the question mark ? is used as a replacement for if :

Depending on the condition company == 'Netscape' , either the first or the second expression after the ? gets executed and shows an alert.

We don’t assign a result to a variable here. Instead, we execute different code depending on the condition.

It’s not recommended to use the question mark operator in this way.

The notation is shorter than the equivalent if statement, which appeals to some programmers. But it is less readable.

Here is the same code using if for comparison:

Our eyes scan the code vertically. Code blocks which span several lines are easier to understand than a long, horizontal instruction set.

The purpose of the question mark operator ? is to return one value or another depending on its condition. Please use it for exactly that. Use if when you need to execute different branches of code.

if (a string with zero)

Will alert be shown?

Yes, it will.

Any string except an empty one (and "0" is not empty) becomes true in the logical context.

We can run and check:

The name of JavaScript

Using the if..else construct, write the code which asks: ‘What is the “official” name of JavaScript?’

If the visitor enters “ECMAScript”, then output “Right!”, otherwise – output: “You don’t know? ECMAScript!”

Demo in new window

Show the sign

Using if..else , write the code which gets a number via prompt and then shows in alert :

• 1 , if the value is greater than zero,
• -1 , if less than zero,
• 0 , if equals zero.

In this task we assume that the input is always a number.

Rewrite 'if' into '?'

Rewrite this if using the conditional operator '?' :

Rewrite 'if..else' into '?'

Rewrite if..else using multiple ternary operators '?' .

For readability, it’s recommended to split the code into multiple lines.

• If you have suggestions what to improve - please submit a GitHub issue or a pull request instead of commenting.
• If you can't understand something in the article – please elaborate.
• To insert few words of code, use the <code> tag, for several lines – wrap them in <pre> tag, for more than 10 lines – use a sandbox ( plnkr , jsbin , codepen …)

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Different Forms of Assignment Statements in Python

• Statement, Indentation and Comment in Python
• Conditional Statements in Python
• Assignment Operators in Python
• Loops and Control Statements (continue, break and pass) in Python
• Different Ways of Using Inline if in Python
• Difference between "__eq__" VS "is" VS "==" in Python
• Augmented Assignment Operators in Python
• Nested-if statement in Python
• How to write memory efficient classes in Python?
• Difference Between List and Tuple in Python
• A += B Assignment Riddle in Python
• Difference between List VS Set VS Tuple in Python
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• Data Classes in Python | Set 5 (post-init)
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• What is the difference between = (Assignment) and == (Equal to) operators

We use Python assignment statements to assign objects to names. The target of an assignment statement is written on the left side of the equal sign (=), and the object on the right can be an arbitrary expression that computes an object.

There are some important properties of assignment in Python :-

• Assignment creates object references instead of copying the objects.
• Python creates a variable name the first time when they are assigned a value.
• Names must be assigned before being referenced.
• There are some operations that perform assignments implicitly.

Assignment statement forms :-

1. Basic form:

This form is the most common form.

2. Tuple assignment:

When we code a tuple on the left side of the =, Python pairs objects on the right side with targets on the left by position and assigns them from left to right. Therefore, the values of x and y are 50 and 100 respectively.

3. List assignment:

This works in the same way as the tuple assignment.

4. Sequence assignment:

In recent version of Python, tuple and list assignment have been generalized into instances of what we now call sequence assignment – any sequence of names can be assigned to any sequence of values, and Python assigns the items one at a time by position.

5. Extended Sequence unpacking:

It allows us to be more flexible in how we select portions of a sequence to assign.

Here, p is matched with the first character in the string on the right and q with the rest. The starred name (*q) is assigned a list, which collects all items in the sequence not assigned to other names.

This is especially handy for a common coding pattern such as splitting a sequence and accessing its front and rest part.

6. Multiple- target assignment:

In this form, Python assigns a reference to the same object (the object which is rightmost) to all the target on the left.

7. Augmented assignment :

The augmented assignment is a shorthand assignment that combines an expression and an assignment.

There are several other augmented assignment forms:

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Java Tutorial

Java methods, java classes, java file handling, java how to, java reference, java examples, java if ... else, java conditions and if statements.

You already know that Java supports the usual logical conditions from mathematics:

• Less than: a < b
• Less than or equal to: a <= b
• Greater than: a > b
• Greater than or equal to: a >= b
• Equal to a == b
• Not Equal to: a != b

You can use these conditions to perform different actions for different decisions.

Java has the following conditional statements:

• Use if to specify a block of code to be executed, if a specified condition is true
• Use else to specify a block of code to be executed, if the same condition is false
• Use else if to specify a new condition to test, if the first condition is false
• Use switch to specify many alternative blocks of code to be executed

The if Statement

Use the if statement to specify a block of Java code to be executed if a condition is true .

Note that if is in lowercase letters. Uppercase letters (If or IF) will generate an error.

In the example below, we test two values to find out if 20 is greater than 18. If the condition is true , print some text:

Try it Yourself »

We can also test variables:

Example explained

In the example above we use two variables, x and y , to test whether x is greater than y (using the > operator). As x is 20, and y is 18, and we know that 20 is greater than 18, we print to the screen that "x is greater than y".

Test Yourself With Exercises

Print "Hello World" if x is greater than y .

Start the Exercise

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