search
String.prototype.includes
Returns true if searchString appears anywhere in the string, otherwise false. Added in ES2015 as a cleaner boolean alternative to indexOf() !== -1.
str.includes(searchString[, position])Parameters
| Parameter | Purpose |
|---|---|
| searchString | String to search for |
| position | Index at which to begin searching (default 0) |
Examples
console.log('hello world'.includes('world'));Prints true
console.log('hello world'.includes('World'));Prints false (case-sensitive)
console.log('hello'.includes('ell', 2));Prints false (starts search at index 2)
console.log('abc'.includes(''));Prints true (empty string always matches)
Gotcha
Does not accept a RegExp — passing one throws a TypeError. Case-sensitive; lowercase both sides for case-insensitive checks.
Related methods
String.prototype.indexOf
Returns the index of the first occurrence of searchValue within the string, or -1 if not found. Search is case-sensitive and starts from fromIndex (default 0).
String.prototype.startsWith
Returns true if the string begins with searchString at the given position (default 0). Added in ES2015 and is more efficient than slice() + === comparisons.
String.prototype.endsWith
Returns true if the string ends with searchString when considered up to endPosition (default str.length). Useful for file extension and suffix checks.
String.prototype.match
Runs a regular expression against the string and returns match information. With the g flag it returns an array of all match strings; without it, an exec-style array with capture groups, index, and input (or null).
String.prototype.matchAll
Returns an iterator of all detailed match results, each including capture groups, index, and input. Added in ES2020 and requires a global (g) RegExp — non-global patterns throw TypeError.