gistfile1.js

var arr = []; var x = [];

for (var i = 0; i < 100; ++i) { x [i] = i };

var d = +new Date;
for (var i = 0; i < 1000; ++i) {
    arr = arr.concat(x);
}
console.log(+new Date - d);


var d = +new Date;
for (var i = 0; i < 1000; ++i) {
    arr.push.apply(arr, x);
}
console.log(+new Date - d);