JavaScript Operators - Comparison Operators

In this JavaScript operators tutorial, learn how to use JavaScript comparison operators that compare two values and return a Boolean value indicating whether the comparison is true

In this tutorial, you will learn how to use JavaScript comparison operators to compare two values.

Introduction to JavaScript comparison operators

To compare two values, you use the comparison operators. The following table illustrates the JavaScript comparison operators:

A comparison operator returns a Boolean value indicating that the comparison is true or not. See the following example:

let r1 = 20 > 10; // true
let r2 = 20 < 10; // false
let r3 = 10 == 10; // true

The comparison operator takes at least two values (or operands). If one of the two values has a different type, JavaScript will perform a conversion based on specific rules before comparing them. We will discuss each rule in detail in the following sections.

Comparing numbers

If the operands are numbers, JavaScript will perform a numeric comparison. For example:

let a = 10, 
    b = 20; 
console.log(a >= b);  // false
console.log(a == 10); // true

This example is straightforward. the variable a is 10, b is 20. The a>=b expression returns and a==10 expression returns true.

Comparing strings

If the operands are strings, JavaScript compares the character codes numerically one by one in the string.

let name1 = 'alice',
    name2 = 'bob';    
let result = name1 < name2;
console.log(result); // true
console.log(name1 == 'alice'); // true

Because JavaScript compares character codes in the strings numerically, you may receive an unexpected result, for example:

let f1 = 'apple',
    f2 = 'Banana';
let result = f2 < f1;
console.log(result); // true

In this example, f2 is less than f1 because the letter B has the character code 66 while the letter a has the character code 97.

To fix this, you must first convert strings into a common format, either lowercase or uppercase and then perform comparison as follows:

let result2 = f2.toLowerCase() < f1.toLowerCase();
console.log(result2); // false

Note that the toLowerCase() is a method of the String object that converts the string itself to lowercase.

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JavaScript values are allocated when things are created (objects, Strings, etc.) and freed automatically when they are no longer used. This process is called Garbage collection.