jsperf

I have used JSperf to test a small sample of code . According to a few articles I came across, both should have similar performance with test2 having a little edge. But here it's the complete opposite. Can someone explain why the huge difference? Edit : I also understand the differences between both of them. Please don't mark this as a duplicate of this or other questions which talk about the semantic differences and do not answer my question regarding performance. Thank you. With the powerful optimizations JavaScript engines are using these days, Micro-benchmarks like this produce somewhat

What is the fastest method, to add a new value at the beginning of a string? Thor Jacobsen var mystr = "Doe"; mystr = "John " + mystr; Wouldn't this work for you? You could do it this way .. var mystr = 'is my name.'; mystr = mystr.replace (/^/,'John '); console.log(mystr); disclaimer: http://xkcd.com/208/ ES6: let after = 'something after'; let text = `before text ${after}`; chirag you could also do it this way "".concat("x","y") Since the question is about what is the fastest method, I thought I'd throw up add some perf metrics. TL;DR The winner, by a wide margin, is the + operator, and

Today I visited jsPerf and now I am wondering… What is “ops/sec”? How many iterations does it do? On what basis does it calculate which is faster? What is the formula behind these calculations? Example: http://jsperf.com/concatenation-vs-join Can anyone tell me? Thanks in advance. John-David Dalton I wrote Benchmark.js , which jsPerf uses. " ops/sec " stands for operations per second. That is how many times a test is projected to execute in a second. A test is repeatedly executed until it reaches the minimum time needed to get a percentage uncertainty for the measurement of less than or equal

I've been looking at the source code of my.class.js to find out what makes it so fast on Firefox. Here's the snippet of code used to create a class: my.Class = function () { var len = arguments.length; var body = arguments[len - 1]; var SuperClass = len > 1 ? arguments[0] : null; var hasImplementClasses = len > 2; var Class, SuperClassEmpty; if (body.constructor === Object) { Class = function () {}; } else { Class = body.constructor; delete body.constructor; } if (SuperClass) { SuperClassEmpty = function() {}; SuperClassEmpty.prototype = SuperClass.prototype; Class.prototype = new