“concat” does not join JavaScript arrays together?

Question

I\'m running the following code on Webkit:

var scriptElements = document.scripts;
var scriptUrls = [];
// URL matching
var regexp = /\\b((?:[a-z][\\w-]+:(?:\         


        

Answer 1

.concat creates a new Array. You need to overwrite the old one.

scriptUrls = scriptUrls.concat(urls);

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Or if you want to keep the original scriptUrls Array, you can .push() the values in.

scriptUrls.push.apply(scriptUrls, urls);

This uses .apply() to convert urls into individual arguments passed to .push(). This way the content of urls is added to scriptUrls as individual items.

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Also, note that .concat() flattens the Array. If you wanted an Array of Arrays, then you'd use scriptUrls.push(urls).

Answer 2

concat does not alter this or any of the arrays provided as arguments but instead returns a "one level deep" copy that contains copies of the same elements combined from the original arrays.

https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Array/concat