RinatValiullov

Простые задачи на яваскрипт

Пропустить теорию и перейти прямо к задачам

Ссылка на учебник: http://learn.javascript.ru

Сразу расскажу про несколько особенностей яваскрипта, о которых может быть не написано (или мало написано) в учебниках, но которые стоит понимать:

Версии яваскрипта

RinatValiullov

Синхронизация настроек Sublime Text 3

RinatValiullov

// Gulp 4
var gulp = require('gulp');
var using = require('gulp-using');
var grep = require('gulp-grep');
var changed = require('gulp-changed');
var del = require('del');
var coffee = require('gulp-coffee');
var less = require('gulp-less');
var coffeelint = require('gulp-coffeelint');
var sourcemaps = require('gulp-sourcemaps');

RinatValiullov

// Определяем зависимости в переменных
var gulp = require('gulp'),
	cache = require('gulp-cache'),
	clean = require('gulp-clean'),
	stream = require('event-stream'),
	size = require('gulp-size'),
	jshint = require('gulp-jshint'),
	concat = require('gulp-concat'),
	uglify = require('gulp-uglify'),
	minifyCSS = require('gulp-minify-css'),

RinatValiullov

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Element

Box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent
• elem.clientLeft, elem.clientTop, elem.clientWidth, elem.clientHeight
• elem.getClientRects(), elem.getBoundingClientRect()

RinatValiullov

While attempting to explain JavaScript's reduce method on arrays, conceptually, I came up with the following - hopefully it's helpful; happy to tweak it if anyone has suggestions.

Intro

JavaScript Arrays have lots of built in methods on their prototype. Some of them mutate - ie, they change the underlying array in-place. Luckily, most of them do not - they instead return an entirely distinct array. Since arrays are conceptually a contiguous list of items, it helps code clarity and maintainability a lot to be able to operate on them in a "functional" way. (I'll also insist on referring to an array as a "list" - although in some languages, List is a native data type, in JS and this post, I'm referring to the concept. Everywhere I use the word "list" you can assume I'm talking about a JS Array) This means, to perform a single operation on the list as a whole ("atomically"), and to return a new list - thus making it much simpler to think about both the old list and the new one, what they contain, and