How to compare strings in JavaScript? [5 Methods]


Written By - Olorunfemi Akinlua
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Introduction

Comparing strings in JavaScript is a common task that is frequently performed in web development. There are a few different ways to compare strings in JavaScript, and the approach you choose will depend on the specific needs of your project.

In this article, we will explore the various techniques for comparing strings in JavaScript. We will cover the built-in methods and operators that are available for comparing strings. Whether you are a beginner or an experienced developer, understanding how to compare strings in JavaScript is an essential skill for working with text data.

 

Method-1: Using the == operator to compare strings

One way to compare strings is to use the == operator. This operator will compare the values of the two strings and return true if they are equal, and false if they are not.

Here is an example where we compare two strings using the == operator.

let str1 = "hello";
let str2 = "hello";

if (str1 == str2) {
    console.log("The strings are equal");
} else {
    console.log("The strings are not equal");
}

Output

The strings are equal

This approach is simple and easy to understand, but it has some limitations. One limitation is that the == operator will perform type coercion, which means that it will attempt to convert the values of the two strings to a common type before making the comparison. Here is an example show the phenomenon

let str1 = "1";
let str2 = 1;

if (str1 == str2) {
    console.log("The strings are equal");
} else {
    console.log("The strings are not equal");
}

Output

The strings are equal

In this case, the == operator will convert the value of str1 to a number (1) before making the comparison, and the strings will be considered equal. This can lead to unexpected results in some cases, and it is generally considered best practice to avoid using the == operator for string comparisons.

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Method-2: Using the === operator to compare strings

A better way to compare strings in JavaScript is to use the === operator. This operator is known as the strict equality operator, and it will only return true if the values of the two strings are equal and of the same type. Using the same code above but with the use of the === operator, we get a different output.

let str1 = "1";
let str2 = 1;

if (str1 === str2) {
    console.log("The strings are equal");
} else {
    console.log("The strings are not equal");
}

Output

The strings are not equal

In this case, the === operator will not perform type coercion, and the strings will be considered not equal because they are of different types (string and number). This is generally the preferred method for comparing strings in JavaScript, as it avoids the potential pitfalls of type coercion.

 

Method-3: Using the localeCompare() method to compare strings

Another way to compare strings in JavaScript is to use the String.prototype.localeCompare() method. This method compares two strings based on the Unicode value of each character, and it returns a number indicating the result of the comparison. A value of 0 indicates that the strings are equal, a value less than 0 indicates that the first string is sorted before the second string, and a value greater than 0 indicates that the first string is sorted after the second string.

Here is an example that compares two strings using the `locale

let str1 = "hello";
let str2 = "world";

let result = str1.localeCompare(str2);

if (result === 0) {
    console.log("The strings are equal");
} else if (result < 0) {
    console.log("The first string comes before the second string");
} else {
    console.log("The first string comes after the second string");
}

Output

The first string comes before the second string

The localeCompare() method is useful when you need to compare strings in a specific language or locale, as it takes into account the various rules and conventions for sorting strings in different languages.

 

Method-4: Using the valueOf() method to compare strings

The String.prototype.valueOf() method returns the primitive value of a string, which can be compared using the == or === operators.

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Here is an example of how to use the valueOf() method to compare two strings (”hello” and “world”).

let str1 = "hello";
let str2 = "world";

if (str1.valueOf() === str2.valueOf()) {
    console.log("The strings are equal");
} else {
    console.log("The strings are not equal");
}

Output

The strings are not equal

 

Method-5: Using the charAt() method to compare strings

Another built-in string method we can use to compare strings in JavaScript is the String.prototype.charAt() method. The String.prototype.charAt() method can be used to compare the characters of two strings one by one by checking the involved character at the specified index.

let str1 = "hello";
let str2 = "Hello";

if (str1.length !== str2.length) {
    console.log("The strings are not equal");
} else {
    let isEqual = true;
    for (let i = 0; i < str1.length; i++) {
        if (str1.charAt(i) !== str2.charAt(i)) {
            isEqual = false;
            break;
        }
    }
    if (isEqual) {
        console.log("The strings are equal");
    } else {
        console.log("The strings are not equal");
    }
}

Output

The strings are not equal

Even though, the only difference in the strings is the capitalized first character because we can compare the character at each index to see if there are equal.

 

Summary

In summary, there are a few different ways to compare strings in JavaScript, and the approach you choose will depend on your specific needs. The == operator is simple and easy to understand, but it can produce unexpected results due to type coercion. The === operator is generally the preferred method for string comparisons, as it avoids the potential pitfalls of type coercion. The String.prototype.localeCompare() method is useful when you need to compare strings in a specific language or locale, as it takes into account the various rules and conventions for sorting strings in different languages. The String.prototype.charAt() method also provides a functional approach to compare the strings character by character.

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It is worth noting that all of these methods are used to compare the values of two strings, rather than the actual strings themselves. In other words, they are comparing the characters that make up the strings, rather than the memory addresses where the strings are stored.

 

References

Equality (==) - JavaScript | MDN (mozilla.org)
Strict equality (===) - JavaScript | MDN (mozilla.org)
String.prototype.localeCompare() - JavaScript | MDN (mozilla.org)
String.prototype.valueOf() - JavaScript | MDN (mozilla.org)
String.prototype.charAt() - JavaScript | MDN (mozilla.org)

 

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