v8

问题 I want to define a read-only object property that asynchronously fetches a value and then returns it using the new EcmaScript 5 getters. However, the property always returns undefined even though magicValue in the example code below is definitively never undefined. Also, when I just return 'xxx'; the printed value is still undefined . It only works when I return outside the callback function. It seems like return is being executed immediately regardless of whether the callback of

问题 While reading on Javascript's prototypes I encountered this behaviour I can't explain. I am testing this in chrome's console (which is V8). var fruit = {taste:'good'}; var banana = Object.create(fruit); console.log(banana.taste); //"good" console.log(banana.__proto__); //Object {taste: "good"} console.log(Object.getPrototypeOf(banana)); //Object {taste: "good"} So far everything is as expected. However if I do this: var drink = Object.create(null); Object.defineProperty(drink, 'taste', {value

问题 In python, I can do the following: name = "bob" print("Hey, %s!" % name) Is there anything similar to that (or Python's .format() ) in JavaScript/NodeJS? 回答1: sprintf should do what you are asking for I think. 回答2: You can use util.format, it's printf like function. 回答3: Another option is template strings For example: const name = "bob"; console.log(`Hey, ${name}!`); 来源： https://stackoverflow.com/questions/10788408/nodejs-string-format-like-python

问题 For example, if we assume the following code: var f = function() { return 'hello world' }; var x = 10; var y = 314; var g = function() { var buf = [], xx = x; while (xx--) buf.append(f() + ' '); return buf.join(''); } I can get the actual "code" as a string of g with g.toString() . However, this does not (obviously) get f and x —members of the closure of g (sorry if I'm not quite using these terms correctly.) Is there some way to query a function for what its closure contains? Ideally I could

问题 In ECMAScript,there is not __proto__ of an object: Array.hasOwnProperty('prototype') //true var arr = new Array() arr.hasOwnProperty('__proto__') //false then, we can find: Object.getOwnPropertyDescriptors(arr) Output: length:{value: 1, writable: true, enumerable: false, configurable: false} __proto__:Object So, I am confused: Does arr has his own property __proto__ ? When I try to do follow things: arr.unshift("2") Where does Js engine find unshift method? Is there any information let Js

问题 I'm using Nodeclipse 0.10 with nodemon, but when I try to debug my script it doesn't stop at any of my breakpoints. I've already seen this and this answer but it hasn't helped. Occasionally, it will stop on the first line of nodemon, other times it gives me a timeout error from the V8 VM, and sometimes it doesn't do anything at all. Here's what I've tried so far: I tried both the "Node application" and the "Node with monitor", neither one works. Removed nodemon from the preferences page, but

问题 The answer to this similar question doesn't solve my problem. Here is the answer from that question: If you decide to use a newer therubyracer gem version, you will no longer have this problem Otherwise: brew tap homebrew/dupes # Thanks Tom brew install apple-gcc42 export CC=/usr/local/Cellar/apple-gcc42/4.2.1-5666.3/bin/gcc-4.2 export CXX=/usr/local/Cellar/apple-gcc42/4.2.1-5666.3/bin/g++-4.2 export CPP=/usr/local/Cellar/apple-gcc42/4.2.1-5666.3/bin/cpp-4.2 brew uninstall v8 gem uninstall

问题 I want to learn how to enable harmony v8 options in Node, and my node version is: $ node -v v5.5.0 Use ES6 destructuring as an example for testing $ cat destructure.js 'use strict' var a, b [a, b] = [1, 2] console.log(a, b) Run it straight gets error as expected. $ node destructure.js /usr/home/mko_io/pure-js-files/destructure.js:3 [a, b] = [1, 2] ^^^^^^ But get the same error, after the flag has been set: $ node --harmony_destructuring destructure.js /usr/home/mko_io/pure-js-files

问题 currently, I found the same JavaScript RegExp might generate different result in different JavaScript Engines, here is an example: In Chrome V8 JS engine, /\x3c/.test("\x3c") --> returns true /\x3c/.test(function() { return "\x3c" }) -->returns ***false*** In rhino1.7.6,I typed the command like this: >java -jar js.jar Rhino 1.7.6 2015 04 15 js> /\x3c/.test(function() { return "\x3c" }) true js> And I tested these two: /\x3c/.test("\x3c") --> returns true /\x3c/.test(function() { return "\x3c"