How Do I Escape Backslashes in JavaScript Strings and Regular Expressions?

Escaping Backslashes in Strings

In JavaScript, the backslash character holds significance within both strings and regular expressions. This creates challenges when attempting to include a standalone backslash in text. To achieve this, it's necessary to escape the backslash using two consecutive ones ().

Strings

When creating strings, the first backslash acts as an escape character, while the second represents the actual backslash. For example:

const str = "\"\I have one backslash\"";
console.log(str); // \I have one backslash

Regular Expressions

Similarly, in regular expressions, two consecutive backslashes are required to match a single backslash. This is because the first backslash serves as an escape character within the regular expression literal. For instance:

const regex = /\/; // Match a single backslash

Using Strings to Create Regular Expressions

When using strings to construct regular expressions, it's important to consider two levels of escaping. First, backslashes must be escaped within the string, and then escaped again within the created regular expression. Consequently, four backslashes are necessary in total.

const regex = new RegExp("\\"); // Matches a single backslash using a string

ES2015 and ES2018 Updates

In recent JavaScript versions, template literals provide an alternative method for including backslashes in strings. The String.raw function can also be employed to achieve this.

const str = String.raw`\apple`; // Valid ES2015 syntax

It's worth noting that template literals should be used cautiously, as they do not support substitutions containing ${ characters. Including ${ inside a template literal will result in the inclusion of the backslash in the string, similar to the example below:

const foo = "bar";
const str = String.raw`\apple${foo}`; // Results in \applebar

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