Which JavaScript Array Duplication Method (Slice vs. For Loop) is Fastest?

Comparing the Speed of Duplicating Arrays in JavaScript: Slice vs. For Loop

In JavaScript, there are two common methods for creating a duplicate of an array: the slice method and a for loop. To conduct a thorough analysis of their respective speeds, various duplication methods have been benchmarked, revealing some surprising results.

Speed Measurements

Benchmarks conducted across different browsers have shown that the fastest method for duplicating an array depends on the browser engine being used. For browsers like Blink (Chrome, Edge), the slice method generally outperforms the for loop, with concat being slightly slower.

However, for browsers with less optimized implementations of slice and concat, such as older versions of Firefox and Internet Explorer, the while loop method emerges as the clear winner.

Example Code

Here are sample scripts you can use to benchmark the methods yourself in your browser's console:

// While loop method
var n = 1000 * 1000;
var start = +new Date();
var a = Array(n);
var b = Array(n);
var i = a.length;
while (i--) b[i] = a[i];
console.log(new Date() - start);

// Slice method
var n = 1000 * 1000;
var start = +new Date();
var a = Array(n);
var b = a.slice();
console.log(new Date() - start);

Considerations

It's important to note that while the slice or for loop methods will duplicate the array itself, the contents of the array are copied by reference and not deeply cloned. This means that changes to either array will be reflected in both.

So, which method should you choose? For most modern browsers, the slice method is the best option. However, if you're targeting older browsers with less optimized JavaScript implementations, the for loop method may perform better.

The above is the detailed content of Which JavaScript Array Duplication Method (Slice vs. For Loop) is Fastest?. For more information, please follow other related articles on the PHP Chinese website!