2.4 KiB
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If-Else Statement |
Introduction
The if
statement executes a statement if a specified condition is true
. If the condition is false
, then the statement inside else
block gets executed.
Note: The else
statement is optional.
if (condition) {
/* do this if condition is TRUE */
} else {
/* do this if condition is FALSE (or not TRUE) */
}
Multiple if...else
statements can be chained to create an else if
clause. This specifies a new condition to test and can be repeated to test multiple conditions, checking until a true statement is presented to execute.
if (condition1) {
/* do something */
} else if (condition2) {
/* do something else */
} else if (condition3) {
/* do something else */
} else {
/* final statement */
}
Note: If you want to execute more than one statement in the if
, else
or else if
part, curly braces are required around the statements:
if (condition) {
/* do */
/* something */
/* with multiple statements */
} else {
/* do something */
/* else */
}
Additional ternary operator
For a simple operation like assigning a value to a variable conditionally you can use a ternary operator, which is a shorthand syntax for an if...else
clause in JavaScript
// Normal if...else
let num = 1;
if (someCondition){
num = 1;
} else {
num = 0;
}
// Using ternary operator
const num = someCondition ? 1 : 2;
// condition ? true case : false case
Examples
Using if...else
:
// If x is equal to 5, then the condition is TRUE. This results in z being set to 7 and q being set to 42.
// If x does not equal to 5, then the condition is FALSE. This results in z being set to 19.
if (x == 5) {
z = 7;
q = 42
} else {
z = 19;
}
Using else if
:
if (x < 10) {
return "Small number";
} else if (x < 50) {
return "Medium number";
} else if (x < 100) {
return "Large number";
} else {
flag = 1;
return "Invalid number";
}
Using if
alone:
// This function can also act as a Boolean
if (x < 30) {
return "true";
}