Most efficient way to concatenate strings JavaScript in a for loop

Question

Let say you have a for loop and you want to build a string in a very specific way using template literals

I've find 2 similar ways to do it.

let text = ''
words = ['Hello', 'world']
for (i = 0; i < n; i++) {
    text += `${words[i]} || `
}

Or

let text = ''
words = ['Hello', 'world']
for (i = 0; i < n; i++) {
    text = `${text}${words[i]} || `
}

Both produce the same output (Hello || world || )

Is any difference in performance or standard?

Add this ['Hello', 'world'].concat('').join(" || ") as a task to measure performance. — Ele
– Ele, Commented Nov 6, 2018 at 18:16
"Which is more efficient" questions often don't age well. Joining arrays instead of repeated string concatenation used to be the right answer, but then browser venders optimized the latter, making that more efficient. The answer will be different from JS engine to JS engine. — Jacob
– Jacob, Commented Nov 6, 2018 at 18:19

Emeeus · Accepted Answer · 2018-11-06 19:04:10Z

1

I would use words.join(" || ")+" || " today is the fastest way, see this http://jsben.ch/DlXOa , as @jacob points out, it is a relative conclusion. But, as a general rule in JavaScript, usually built-in methods are faster.

answered Nov 6, 2018 at 19:04

Emeeus

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