In JavaScript, there isn't a distinct data structure referred to as an "associative array." Instead, developers often use objects to achieve similar functionality. Key-value pairs Objects in JavaScript are collections of key-value pairs, where the keys (also called property names) are strings ...
//map.jsfunctionusageSize(){constused=process.memoryUsage().heapUsed;returnMath.round(used/1024/1024*100)/100+'M';}global.gc();console.log(usageSize());// ≈ 3.23Mletarr=newArray(5*1024*1024);constmap=newMap();map.set(arr,1);global.gc();console.log(usageSize());// ≈ 43.22Mar...
分别执行node --expose-gc map.js和node --expose-gc weakmap.js。可以很明显地看到区别:在arr被置为null后,Map并没有释放Array,而WeakMap释放了。原因正如上文所示:Map是强引用,arr清除后依旧保留了对new Array(1024 * 1024)的引用指向,而WeakMap并没有保留,因此垃圾回收机制可以照常执行。 再回到WeakRef。W...
等价于 lodashflatten功能: constarray = [1, [2, [3]]]; array.flat();// -> [1, 2, [3]] 还支持自定义深度,如果支持Infinity无限层级: constarray = [1, [2, [3]]]; array.flat(Infinity);// -> [1, 2, 3] 这样我们就可以配合.map使用: [2,3,4].map(duplicate).flat(); 因为这...
What's the fastest way to loop through an array in JavaScript? Ask Question Asked 13 years, 6 months ago Modified 26 days ago Viewed 355k times 323 I learned from books that you should write for loop like this: for(var i=0, len=arr.length; i < len; i++){ // blah blah ...
I was asked recently what was the most efficient way to reverse an array in JavaScript. At the moment, I suggested using a for loop and fiddling with the array but then realized there is a native Array.reverse() method. For curiosity's sake, can anyone help me explore this by showing ...
It allows you to quickly and efficiently group items in a collection based on a key derived from each item. The result is a new object where each key corresponds to a group, and the value is an array of items that belong to that group. Let’s say you have an array of people, and...
More on JavaScriptHow to Use the Ternary Operator in JavaScript3. Array to Argumentsfunction multiply(number1, number2, number3) { console.log(number1 * number2 * number3); } let numbers = [1,2,3]; multiply(...numbers); Instead of having to pass each element like numbers[0], number...
You pass a callback function into theforEach()method. The callback itself accepts three arguments: the current item in the loop, the index of the current item in the loop, and the array itself. All three are optional, and you can name them anything you want. ...
The difference between using Array.of() and the Array constructor is how they both handle a single integer argument: const x = Array.of(3); const y = new Array(3); console.log(x); // output: [3] console.log(