String.prototype.search()

regexp

A regular expression object, or any object that has a Symbol.search method.

If regexp is not a RegExp object and does not have a Symbol.search method, it is implicitly converted to a RegExp by using new RegExp(regexp).

The index of the first match between the regular expression and the given string, or -1 if no match was found.

The implementation of String.prototype.search() doesn't do much other than calling the Symbol.search method of the argument with the string as the first parameter. The actual implementation comes from RegExp.prototype[Symbol.search]().

The g flag of regexp has no effect on the search() result, and the search always happens as if the regex's lastIndex is 0. For more information on the behavior of search(), see RegExp.prototype[Symbol.search]().

When you want to know whether a pattern is found, and also know its index within a string, use search().

• If you only want to know if it exists, use the RegExp.prototype.test() method, which returns a boolean.
• If you need the content of the matched text, use String.prototype.match() or RegExp.prototype.exec().

The following example searches a string with two different regex objects to show a successful search (positive value) vs. an unsuccessful search (-1).

const str = "hey JudE";
const re = /[A-Z]/;
const reDot = /[.]/;
console.log(str.search(re)); // returns 4, which is the index of the first capital letter "J"
console.log(str.search(reDot)); // returns -1 cannot find '.' dot punctuation

• Polyfill of String.prototype.search in core-js with fixes and implementation of modern behavior like Symbol.search support
• Regular expressions guide
• String.prototype.match()
• RegExp.prototype.exec()
• RegExp.prototype[Symbol.search]()