Run results for: Big Array prepend

Run details:

User agent: Mozilla/5.0 (iPhone; CPU iPhone OS 18_3_2 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.3.1 Mobile/15E148 Safari/604.1

Browser: Mobile Safari 18

Operating system: iOS 18.3.2

Device Platform: Mobile

Date tested: one year ago

Unshift

34K/s

Spread Operator

29K/s

Unshift without mutation

28K/s

Prepend function

12K/s

View exact numbers

Test name	Executions per second
✓ Unshift	34,056 Ops/sec
Spread Operator	28,928 Ops/sec
Unshift without mutation	27,897 Ops/sec
Prepend function	11,977 Ops/sec

Script Preparation code:

var a;
var prependArray = function(value, oldArray) {
    var i, len = oldArray.length + 1,
        newArray = new Array(len);
    newArray[0] = value;
    for (i = 0; i < len; ++i) {
        newArray.push(oldArray[i]);
    }
    return newArray;
}

Tests:

Spread Operator
a = new Array(10000).fill().map((_, i) => i) a = [0, ...a];
Unshift
a = new Array(10000).fill().map((_, i) => i) a.unshift(0);
Unshift without mutation
a = new Array(10000).fill().map((_, i) => i) a.slice(0).unshift(0);
Prepend function
a = new Array(10000).fill().map((_, i) => i) prependArray(0, a);