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Learn how to use conditional statements in JavaScript to perform different actions for different decisions. See the syntax, examples, and exercises of if, else, and else if.
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JavaScript also contains a conditional operator that assigns...
- If Else Else If
The if/else statement executes a block of code if a...
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- Overview
- Syntax
- Description
- Examples
- Browser compatibility
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.
condition
An expression that is considered to be either truthy or falsy.
statement1
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.
statement2
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.
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.
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.
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- JavaScript if Statement. The syntax of the if statement is: if (condition) { // the body of if } The if statement evaluates the condition inside the parenthesis ().
- JavaScript if... else statement. An if statement can have an optional else clause. The syntax of the if... else statement is: if (condition) { // block of code if condition is true } else { // block of code if condition is false }
- JavaScript if... else if statement. The if... else statement is used to execute a block of code among two alternatives. However, if you need to make a choice between more than two alternatives, if...
- Nested if... else Statement. You can also use an if... else statement inside of an if... else statement. This is known as nested if... Example 4: Nested if...
Learn how to use if...else statements to execute different blocks of code based on conditions. See examples of if...else, if...else if...else, and switch statements, and how to validate input data.
May 31, 2024 · Learn how to use if-else statement and other conditional statements in JavaScript to execute code based on a condition. See syntax, flowchart, and examples of if, if-else, nested-if, and if-else-if ladder statements.
The if...else...if statement checks the conditions from top to bottom and executes the corresponding block if the condition is true. The if...else...if statement stops evaluating the remaining conditions as soon as a condition is true. For example, if the condition2 is true, the if...else...if statement won’t evaluate the condition3.
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Dec 7, 2022 · Learn how to use if, else, else if and conditional operator ? to perform different actions based on different conditions in JavaScript. See examples, syntax, rules and tips for readability.
