javascript-objects

问题 I have a JavaScript class like this: Dog = (function() { var name; function setName(_name) { name = _name; } return { setName: setName, name: name }; })(); When I run: Dog.setName('Hero'); Dog.name is always undefined. I am certainly missing something about JS scoping, but what? 回答1: You are returning an object where name property has a value of name at that point in time (which is undefined). The name property of the returned object is not somehow dynamically updated when the name variable

问题 I have severel Objects containing one sort of data: Prices: 'btc-usd' : 2640, 'ltc-usd': 40, ... Amount of Crypto: 'btc-usd': 2.533, 'ltc-usd': 10.42, ... How can I take these Objects and create an Array of Objects like: [ { name: 'Bitcoin', amount: 2.533, value: 2640, id: 'btc-usd' }, { name: 'Litecoin', amount: 10.42, value: 40, id: 'ltc-usd' }, ... ] Thanks a lot for your help! 回答1: You could map the keys of one of the objects to produce a new array of objects. You just have to make sure,

问题 This question already has answers here : What does “the prototype belongs to the class not the instance” mean in javascript? (3 answers) Closed 5 years ago . function NamedRoundedBlock(){ var name = this.makeFeild("name"); name.className = "Block NamedRound name"; this.element.className = "Block NamedRound root"; this.element.appendChild(name); } NamedRoundedBlock.prototype = new Block(); NamedRoundedBlock.prototype.constructor = NamedRoundedBlock; There's the code, anyone know what I've done

问题 I've been getting more into oop with js (I'm classically trained in Java) and I have four boxes. I want to do something like this: <div class="box"><\div> <div class="box"><\div> <div class="box"><\div> <div class="box"><\div> Function Box(){ //PRIVATE VAR var count=0; } Box.prototype.move = function(){ this.css({left:50}); } Box.prototype.click= function(){ this.count++; } //create new instances of box and assign or connect to the four HTML elements For (var i = 0; i < $('.box').length; i++)

问题 I've been getting more into oop with js (I'm classically trained in Java) and I have four boxes. I want to do something like this: <div class="box"><\div> <div class="box"><\div> <div class="box"><\div> <div class="box"><\div> Function Box(){ //PRIVATE VAR var count=0; } Box.prototype.move = function(){ this.css({left:50}); } Box.prototype.click= function(){ this.count++; } //create new instances of box and assign or connect to the four HTML elements For (var i = 0; i < $('.box').length; i++)

问题 If I understand correctly, in code below exists recursive reference: var object = {} object.nested = object; console.log(object) In console I can see infinite reference. So, how does interpreter optimizes this case ? How does this reference works ? Does it cause the memory leaks ? Does it exists depth limit ? Plunker: http://plnkr.co/edit/QbR3o8cGnXU924nNs0cE 来源： https://stackoverflow.com/questions/40452539/javascript-does-it-exists-depth-limit-when-object-has-reference-to-itself-how

问题 I need to import JSON data and pull out specific things from it and am having trouble doing it. This is the sample data: { "0bEiO5zcBCHv3Wd2lxHjjRepB":{ "name":"math", "credits":4, "professors":[ "Samatha" ], "description":"come and learn some math", "prereqs":"", "comment":"", "maxEnrollment":100, "times":[ { "day":2, "start":900, "end":1100 }, { "day":4, "start":900, "end":1100 } ], "departments":[ "mathematics" ], "submitted":true }, "BsSbrbjTH5FyV7gWdPjeDPqpw":{ "name":"biology", "credits

问题 I have a nested object and want to remove all key/value pairs if the value is null or undefined. I've managed to get the below code working but it doesn't check the nested key/value pairs and wondered if someone could help me figure out what needs adding to the code please? var myObj = { fName:'john', lName:'doe', dob:{ displayValue: null, value: null }, bbb:null }; function clean(obj) { for (var propName in obj) { if (obj[propName] === null || obj[propName] === undefined || obj[propName] ===

问题 If I have a bunch of objects, and within these objects is the string "id" (which is the same as the object name) how can I use this string to reference the object? Example: //These objects are tests - note the id's are the same as the object name var test1 = { id : "test1", data : "Test 1 test 1 test 1" } var test2 = { id : "test2", data : "Test 2 test 2 test 2" } /* ----- My Function ----- */ var myObj = null; function setMyObj(obj){ myObj = obj; } setMyObj(test1); /* ----- My Function -----

问题 I'm pretty new to JS and i'm trying to learn some basics in functions. I'm facing a problem, I've created a function like this: function someName (element, settings={i:"#1d252c", i2:"#fff"}) { ....... } If i call the function as someName(element) . i and i2 retain their values, however If i call it like someName(element,{i:"#3acbda"}) , the value of i does change however the value of i2 is undefined, So how do i assign the default value to a property when the settings object is no longer the