What's the best way to convert a number to a string in JavaScript? [closed]

Answer 1

The only valid solution for almost all possible existing and future cases (input is number, null, undefined, Symbol, anything else) is String(x). Do not use 3 ways for simple operation, basing on value type assumptions, like "here I convert definitely number to string and here definitely boolean to string".

Explanation:

String(x) handles nulls, undefined, Symbols, [anything] and calls .toString() for objects.

'' + x calls .valueOf() on x (casting to number), throws on Symbols, can provide implementation dependent results.

x.toString() throws on nulls and undefined.

Note: String(x) will still fail on prototype-less objects like Object.create(null).

If you don't like strings like 'Hello, undefined' or want to support prototype-less objects, use the following type conversion function:

/**
 * Safely casts any value to string. Null and undefined are converted to ''.
 * @param  {*} value
 * @return {string}
 */
function string (str) {
  return value == null ? '' : (typeof value === 'object' && !value.toString ? '[object]' : String(value));
}

Answer 2

I like the first two since they're easier to read. I tend to use String(n) but it is just a matter of style than anything else.

That is unless you have a line as

var n = 5;
console.log ("the number is: " + n);

which is very self explanatory

Answer 3

Method toFixed() will also solves the purpose.

var n = 8.434332;
n.toFixed(2)  // 8.43

Answer 4

Explicit conversions are very clear to someone that's new to the language. Using type coercion, as others have suggested, leads to ambiguity if a developer is not aware of the coercion rules. Ultimately developer time is more costly than CPU time, so I'd optimize for the former at the cost of the latter. That being said, in this case the difference is likely negligible, but if not I'm sure there are some decent JavaScript compressors that will optimize this sort of thing.

So, for the above reasons I'd go with: n.toString() or String(n). String(n) is probably a better choice because it won't fail if n is null or undefined.

Answer 5

Other answers already covered other options, but I prefer this one:

s = `${n}`

Short, succinct, already used in many other places (if you're using a modern framework / ES version) so it's a safe bet any programmer will understand it.

Not that it (usually) matters much, but it also seems to be among the fastest compared to other methods.

Answer 6

You can call Number object and then call toString().

Number.call(null, n).toString()

You may use this trick for another javascript native objects.