JavaScript RegExp global Property

What Is global?

regex.global is a read-only boolean. It is true when the RegExp was created with the g flag — so searches can find all matches, not only the first.

/cat/.global      → false
/cat/g.global     → true

with g:
  exec() / test() advance lastIndex
  can find every match in a loop

without g:
  exec() always returns the first match again

flags are fixed at creation — cannot set .global = true

How to Use global

Add g when you create the regex, then read .global or rely on lastIndex.

1. Create the regex with g: /pattern/g or new RegExp(pattern, "g").
2. Read regex.global — it should be true.
3. Use exec() in a loop (or match / matchAll) to get every hit.
4. Reset regex.lastIndex = 0 before searching the same string again from the start.

Pseudocode

regex = /pattern/g     // global = true
str = text to search

while (match = regex.exec(str)) is not null:
    use match
    // lastIndex moved forward automatically

// restart from the beginning:
regex.lastIndex = 0

Cheat Sheet

Keep these facts handy when using the g flag.

Live Preview

Compare a non-global and global regex on the same string.

regex = /\d+/
global → false

exec #1 → "1" (index 1)
exec #2 → "1" (index 1)  /* same first match again */

JavaScript Examples

Short, copy-ready snippets. Open DevTools Console, or use Try It Yourself for a live editor.

const a = /cat/;
const b = /cat/g;
const c = new RegExp("cat", "gi");

console.log(a.global); // false
console.log(b.global); // true
console.log(c.global); // true
console.log(c.flags);  // "gi"

false
true
true
gi

const str = "a1 a2";
const once = /\d+/;
const all = /\d+/g;

console.log(once.exec(str)[0]); // "1"
console.log(once.exec(str)[0]); // "1"  (repeats)

console.log(all.exec(str)[0]);  // "1"
console.log(all.exec(str)[0]);  // "2"  (advances)

1
1
1
2

const regex = /\d+/g;
const str = "A12 B34 C5";
const found = [];
let match;

while ((match = regex.exec(str)) !== null) {
  found.push(match[0]);
}

console.log(found.join(", ")); // "12, 34, 5"
console.log(regex.global);     // true

12, 34, 5
true

Performance Notes

Global search walks the string once across the loop. Prefer a non-global regex when you only need the first match — clearer and no lastIndex state.

Key Takeaways