ecmascript-5

问题 I have two arrays which I want to compare and check if there is an deleted item in one of these arrays. If there is show me the difference (deleted item) Here is the code below how I would like to achieve this: var completedList = [{id:1},{id:2},{id:3},{id:4},{id:7},{id:8}]; var invalidList = [{id:3},{id:4},{id:5},{id:6}]; // filter the items from the invalid list, out of the complete list var validList = completedList.map((item) => { console.log(item.id) return item.id; //console.log

问题 Identifying which objects are which is complicated in JavaScript, and figuring out which objects are arrays has something of a hacky solution. Fortunately, it manages to work in both of the following cases: Object.prototype.toString.call([]); // [object Array] Object.prototype.toString.call(new Array()); // [object Array] Great, no [object Object] in sight! Sadly, this method still manages to fail with this: var arr = Object.create(Array.prototype); Object.prototype.toString.call(arr); //

问题 I'm trying to limit the entries to a specific format. If the entry has 5500 or 5100 such as 01\01-5500-000-00 then I want to have this: ^[0-9]{2,}\\[0-9]{2}\-[0-9]{4}\-[0-9]{3}\-$ But if the entry has anything other than 5500 or 5100 I want to have this: ^[0-9]{2,}\\[0-9]{2}\-[0-9]{4}\-[0-9]{3}\-[0-9]{2}$ How can this be accomplished with the if then else idea? 回答1: Conditional regex syntax is not supported by JavaScript regex engine, but it can be worked around with a non-capturing group

问题 This question already has answers here : Why does ++[[]][+[]]+[+[]] return the string “10”? (9 answers) (![]+[])[+[]]… Explain why this works (1 answer) Closed 6 years ago . While reading this article posted on dzone I found a snippet of JavaScript originally posted on Twitter by Marcus Lagergren. The following code apparently prints the string "fail" (![]+[])[+[]]+(![]+[])[+!+[]]+([![]]+[][[]])[+!+[]+[+[]]]+(![]+[])[!+[]+!+[]]; This involves implicit type casting and I'm trying to understand

问题 I have a line of legacy code to split a string on semi-colons: var adds = emailString.split(/;+/).filter(Boolean); What could the filter(Boolean) part do? 回答1: filter(Boolean) will only keep the truthy values in the array. filter expects a callback function, by providing Boolean as reference, it'll be called as Boolean(e) for each element e in the array and the result of the operation will be returned to filter . If the returned value is true the element e will be kept in array, otherwise it

问题 When I put this array into my Server/servermethods.js I get this error: server/serverMethods.js:4:1783: Unexpected token ILLEGAL I'm using meteor, but I think this is some sort of javascript error. I've checked, it's not missing commas or apostrophes. var RedemtionCodes =['27GP','2DNW','2DPH','2SE7’,‘2U29’,‘2V5Q’,‘2WNY’,‘2XU6’,‘35W4’,‘3BC4’,‘3H3P’,‘3LQG’,‘3NHL’,‘3T8Y’,‘3UXV’,‘3ZG7’,‘48RD’,‘48WS’,‘4AYE’,‘4E6V’,‘4J36’,‘4KMM’,‘4QNA’,‘4RHV’,‘4RSV’,’4WZK’,’536G’,’567K’,’58EN’,’58NC’,’5B2Z’,’5DU8’,

问题 I have deployed a js application on heroku that uses meteor. The build works on localhost but fails on the heroku server. I checked the logs and found this: .js:312:12) 2017-03-18T03:29:07.070711+00:00 app[web.1]: const unicodeNormalizePath = (path) => { 2017-03-18T03:29:07.074825+00:00 app[web.1]: at Module.require (module.js:364:17) 2017-03-18T03:29:07.074821+00:00 app[web.1]: SyntaxError: Unexpected token > 2017-03-18T03:29:07.074824+00:00 app[web.1]: at Module.load (module.js:356:32) 2017

问题 Laravel Mix does not seem to transpile vendor.js and manifest.js to ES5. It fails on iPhone Safari and IE 11. IE DevTools shows these errors: And it appears that it still has ES6 features: The other files seem to transpile such as app.js and the chunks. Here's my webpack.mix.js let mix = require('laravel-mix'); let options = { processCssUrls: false, } let config = { output: { chunkFilename: 'assets/js/chunks/[name].js', publicPath: '/' } } if (mix.inProduction()) { config.output.chunkFilename

问题 I'm grokking my way through ES6 and I ran into Modules (nice!) and in learning, I am trying to see if I can use them in the browser without WebPack (which I haven't learned yet). So, I have the following files/folder structure in my JS directory js - lib (for complied es6 via Babel) - mods (compiled modules) - module.js (compiled via Babel) - app.js (imports modules, attached to index.html) - src (for "raw" es6) - mods (es6 modules) - module.js (es6 module) - app.js (imports modules) In js

问题 Here's my gulp task to compile my ES6 code into a single ES5 file. I use classes and modules ( import , export ) in ES6. gulp.src(paths.scripts) .pipe(sourcemaps.init()) .pipe(babel({ presets: ['es2015'] })) .pipe(concat('all.js')) .pipe(sourcemaps.write('.')) .pipe(gulp.dest('./www/js')); However, because Babel compiles ES6 import directives into require commands, and require will attempt to request a file, the request files are failing because all the ES5 code is concatted into one file,