Insert a String at a Specific Index

Name: Insert a String at a Specific Index
Uploaded: 2026-09-27T17:24:21+00:00
Duration: 19 min 11 s
Description: How Can I Insert a String at a Specific Index of Another String? Var Txt1 = "Foo Baz" Suppose I Want to Insert "Bar " After the "Foo" How Can I Achieve That? I...

Question

How can I insert a string at a specific index of another string?

 var txt1 = "foo baz"

Suppose I want to insert "bar " after the "foo" how can I achieve that?

I thought of substring(), but there must be a simpler more straight forward way.

Accepted Answer

Inserting at a specific index (rather than, say, at the first space character) has to use string slicing/substring:

var txt2 = txt1.slice(0, 3) + "bar" + txt1.slice(3);

Accepted Answer

You could prototype your own splice() into String.

Must Read

Polyfill

if (!String.prototype.splice) {
    /**
     * {JSDoc}
     *
     * The splice() method changes the content of a string by removing a range of
     * characters and/or adding new characters.
     *
     * @this {String}
     * @param {number} start Index at which to start changing the string.
     * @param {number} delCount An integer indicating the number of old chars to remove.
     * @param {string} newSubStr The String that is spliced in.
     * @return {string} A new string with the spliced substring.
     */
    String.prototype.splice = function(start, delCount, newSubStr) {
        return this.slice(0, start) + newSubStr + this.slice(start + Math.abs(delCount));
    };
}

Insert a String at a Specific Index

18 Answers

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Polyfill

Sophia Al-Mansoor