TypeScript - replace first 3 characters in string

In this article, we would like to show you how to replace the first 3 characters in string in TypeScript.

Quick solution

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const text: string = 'ABCD';

const result: string = 'xyz' + text.slice(3);

​

console.log(result); // xyzD

or:

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const text: string = 'ABCD';

const replacer: string = 'xyz';

​

const result: string = replacer.concat(text.slice(3));

​

console.log(result); // xyzD

or:

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const text: string = 'ABCD';

const result: string = text.replace(/^.{3}/g, 'xyz');

​

console.log(result); // xyzD

In this example, we use string slice() method to remove the first 3 characters of the text string. Then with + operator we add the remainder of the text to the replacer.

Runnable example:

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const text: string = 'ABCD';

const replacer: string = 'xy';

​

const result: string = replacer + text.slice(3);

​

console.log(result); // xyD

Output:

xxxxxxxxxx

xyD

Note:

The replacer for the three removed characters may cosist of any number of characters, not exactly 3.

In this example, we use string slice() method to remove the first 3 characters of the text string. Then with concat() method we add the remainder of the text to the replacer.

Runnable example:

xxxxxxxxxx

const text: string = 'ABCD';

const replacer: string = 'xy';

​

const result: string = replacer.concat(text.slice(3));

​

console.log(result); // xyD

Output:

xxxxxxxxxx

xyD

Note:

The replacer for the two removed characters may cosist of any number of characters, not exactly 3.

In this example, we use string replace() with /^.{3}/g regex to replace the first 3 characters in the text string.

Regex explanation:

• ^ - matches the beginning of the string,
• . - matches any character except linebreaks,
• {3} - matches the specified quantity of the previous token (in our case the .).

Runnable example:

xxxxxxxxxx

const text: string = 'ABCD';

const result: string = text.replace(/^.{3}/g, 'xyz');

​

console.log(result); // xyzD

Output:

xxxxxxxxxx

xyzD