Array.prototype.toString() turns an array into a comma-separated string. It is the same as join() with the default comma — and does not mutate the array.
array.toString()
→ "a,b,c" (comma, no spaces)
same as join() (default separator)
read-only
"Hi: " + arr → calls toString automatically
custom separator? → use join(" | ")Call array.toString. Start with this line.
array.toString()| Call | What it does |
|---|---|
array.toString() | Primary signature. |
array.toString(...) | Call with the arguments your case needs. |
Built into JavaScript. Call toString(...) on an array instance — no import required.
array.toString()| Parameter | Description |
|---|---|
| Array | Required. Source values |
| Return Value | Description |
|---|---|
| * | Comma-separated string |
Turn a color list into one line of text.
const colors = ["red", "green", "blue", "yellow"];
const text = colors.toString();
console.log(text);
// "red,green,blue,yellow"toString(). Elements are joined with commas.red,green,blue,yellow.colors still has four items.toString() in ConcatenationJavaScript calls toString() when you mix an array with a string.
const days = ["Mon", "Tue", "Wed"];
console.log("Days: " + days);
// "Days: Mon,Tue,Wed"
console.log(String(days));
// "Mon,Tue,Wed""Days: " + days needs a string result.toString().String(days) is explicit. Same comma list without a prefix.toString() vs join()Need readable spacing? Use join with a custom separator.
const colors = ["red", "green", "blue"];
console.log(colors.toString());
// "red,green,blue"
console.log(colors.join(" | "));
// "red | green | blue"toString is fixed. Always commas, no options.join is flexible. Pass any separator string.join() with no args matches toString().toString; pretty text → join.Array.prototype.toString() has been available since ES3 and is one of the most widely supported JavaScript methods.
Supported in every browser and Node.js version—including very old environments. Behavior is identical across platforms.
Bottom line: Safe everywhere. Remember its limits with objects and locale-sensitive numbers.
Learn how to add one or more elements at the beginning of an array.
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