JavaScript: String.prototype.replaceAll

New in JS2021.

Original string is not changed by this function.

str.replaceAll(str1, repStr)

Replace all occurrences of string str1 by repStr. (No regex is used.)

Return a new string.

console.log(
  "a.b.c".replaceAll(".", "-") === "a-b-c",
);

str.replaceAll(str1, repFunc)

Replace all occurrences of string str1 by a function repFunc. (No regex is used.)

Return a new string.

The function is called for each match. See: JavaScript: Regex Replacement Function Arguments

const ff = ((x) => {
  return x + x;
});

console.log(
  "a.b.c".replaceAll(".", ff) === "a..b..c",
);

str.replaceAll(regexObj, repStr)

Use regex to replace all occurrences. regexObj must have the RegExp Flag g.

Return a new string.

In the replacement string repStr, {$1, $2, etc} refers to captured group. [see JavaScript: Regex Replacement String Dollar Sign Sequence]

/* replaceAll basic example */
console.log(
  "xy x1 x2".replaceAll(/x(\d+)/g, "y$1") === "xy y1 y2",
);

str.replaceAll(regex, repFunc)

The function repFunc's return value is used as the replacement string.

The function is called for each match. See: JavaScript: Regex Replacement Function Arguments

/*
example of RegExp replace, using function as replacement.

add a alt attribute to a HTML image tags, but convert any lowline char to space.

for example

<img src="my_cat.jpg">
become
<img src="my_cat.jpg" alt="my cat">

*/

const xtext = `
<img src="black_cat.jpg">
<img src="dog.jpg">
<img src="red-bird.jpg">
`;

const xrg = /<img src="([-\w]+)\.jpg">/g;

const fRep = ((
  Ms,
  C1,
) => (`<img src="${C1}.jpg" alt="${C1.replace(/_/g, " ")}">`));

const yy = xtext.replaceAll(xrg, fRep);

console.log(
  yy === `
<img src="black_cat.jpg" alt="black cat">
<img src="dog.jpg" alt="dog">
<img src="red-bird.jpg" alt="red-bird">
`,
);

Examples

With captured group:

/* add alt attribute to a HTML image tags */

const xx = `
<img src="cat.jpg">
<img src="dog.jpg">
<img src="mouse.jpg">
`;

const yy = xx.replaceAll(
  /<img src="([-\w]+)\.jpg">/g,
  '<img src="$1.jpg" alt="$1">',
);

console.log(
  yy === `
<img src="cat.jpg" alt="cat">
<img src="dog.jpg" alt="dog">
<img src="mouse.jpg" alt="mouse">
`,
);