Evaluating JavaScript code via eval() and new Function()
This blog post examines how one can dynamically evaluate code in JavaScript. eval(str) evaluates the JavaScript code in str. For example: > var a = 12; > eval('a + 5') 17 Note that eval() parses in statement context [1]: > eval('{ foo: 123 }') // code block 123 > eval('({ foo: 123 })') // object literal { foo: 123 } eval() in strict mode For eval(), you really should use strict mode [2]. In sloppy
An introduction to JSDoc
Check out my book (free online): “Speaking JavaScript”. Updated version of this blog post: chapter “JSDoc: Generating API Documentation”. Update 2011-08-19. Tweet from JSDoc’s creator, Michael Mathews: Awesome article about JSDoc. I learned (er remembered) a few things from reading it myself! via @rauschma 2ality.com/2011/08/jsdoc-intro.html JSDoc is the de facto standard for documenting JavaScrip
Classes in ECMAScript 6 (final semantics)
Warning: This blog post is outdated. Instead, read chapter “Classes” in “JavaScript for impatient programmers”. Recently, TC39 decided on the final semantics of classes in ECMAScript 6 [1]. This blog post explains how their final incarnation works. The most significant recent changes were related to how subclassing is handled. Overview # class Point { constructor(x, y) { this.x = x; this.y = y; }
ES6 generators in depth
This blog post is outdated. Please read chapter “Generators” in “Exploring ES6”. This blog post is part of a series on iteration in ES6: Iterables and iterators in ECMAScript 6 ES6 generators in depth Generators, a new feature of ECMAScript 6 [1], are functions that can be paused and resumed. This helps with many applications: iterators, asynchronous programming, etc. This blog post explains how g
ECMAScript 6: new OOP features besides classes
This blog post is outdated. Please read chapter “New OOP features besides classes” in “Exploring ES6”. Classes [1] are the major new OOP feature in ECMAScript 6 [2]. However, it also includes new features for object literals and new utility methods in Object. This blog post describes them. New features of object literals # Method definitions # In ECMAScript 5, methods are properties whose values
Variables and scoping in ECMAScript 6
Updated version of this blog post: Chapter “Variables and scoping” in “Exploring ES6”. This blog post examines how variables and scoping are handled in ECMAScript 6 [1]. Block scoping via let and const # Both let and const create variables that are block-scoped – they only exist within the innermost block that surrounds them. The following code demonstrates that the let-declared variable tmp only
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