String.prototype.search()

The search() method executes a search for a match between a regular expression and this String object.

regexp

A regular expression object.

If a non-RegExp object regexp is passed, it is implicitly converted to a RegExp with new RegExp(regexp).

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

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 similar test() method on the RegExp prototype, which returns a boolean.)

For more information (but slower execution) use match() (similar to the regular expression exec() method).

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

let str = "hey JudE"
let re = /[A-Z]/g
let reDot = /[.]/g
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

• Using regular expressions in JavaScript
• String.prototype.match()
• RegExp.prototype.exec()