js RegExp why not always one result?

Question

JavaScript

I don't understand why using one template and one text does not always produce the same result?

Answer 1

RegExp in JavaScript saves its state between calls. Since the expression contains the global match flag g, the search continues after the next match found.
An instance of a Regexp object has a lastIndex property that allows you to read/write the index at which the next match will start. It will help you figure out:

var RE = /([A-z0-9])/g;
console.log([
  RE.lastIndex, RE.test("aaaa"), // 0,true
  RE.lastIndex, RE.test("aaaa"), // 1,true
  RE.lastIndex, RE.test("aaaa"), // 2,true
  RE.lastIndex, RE.test("aaaa"), // 3,true
  RE.lastIndex, RE.test("aaaa"), // 4,false
  RE.lastIndex, RE.test("aaaa"), // 0,true
]);

Answer 2

Due to /g
https://stackoverflow.com/questions/1520800/why-re...