Is JavaScript\'s Array.sort() Method Stable Across All Browsers?

Stability of Array.sort() Method Across Browsers

Introduction

Array sorting is a fundamental operation in JavaScript. However, the stability of the Array.sort() method varies across different browsers.

ECMA Script and Stability

The ECMA Script specification does not define a specific sorting algorithm or specify whether the sort should be stable. This means different browsers may implement different approaches, resulting in varying stability characteristics.

Stability Across Specific Browsers

• IE 6-8: Stable
• Firefox < 3: Unstable
• Firefox >= 3: Stable
• Chrome < 70: Unstable
• Chrome >= 70: Stable
• Opera < 10: Unstable
• Opera >= 10: Stable
• Safari 4: Stable
• Edge (large arrays): Unstable

Example Test Case

To demonstrate the stability of the sort method, a test case involving pairs of values can be created:

<code class="javascript">function Pair(_x, _y) {
    this.x = _x;
    this.y = _y;
}
function pairSort(a, b) {
    return a.x - b.x;
}
var check = [];
for (var i = 0; i < 100; ++i) {
    check.push(new Pair(Math.random() * 3 + 1, ++y));
}
check.sort(pairSort);</code>

If the sort is stable, the values will be sorted based on their x values first, and then by their y values, such that the original order of values with the same x value is preserved. Conversely, an unstable sort may result in different orders for values with the same x value.

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