JavaScript: Variables (ES6)
Setup Project
- mkdir /Fundamentals
- cd Fundamentals
- npm init
- defaults
- npm install –save-dev babel-cli
- npm install –save-dev babel-preset-es2015 babel-preset-stage-2
- touch variables.js
- atom .
package.json
{
“name”: “Fundamentals”,
“version”: “1.0.0”,
“description”: “”,
“main”: “variables.js”,
“scripts”: {
“test”: “echo \”Error: no test specified\” && exit 1″,
“start”: “nodemon variables.js –exec babel-node –presets es2015,stage-2”
},
“author”: “”,
“license”: “ISC”,
“devDependencies”: {
}
}
[/code]
variables.js
[code language=”javascript”]
"use strict";
var firstname = "Jon";
var lastname = "Doe";
var age = 21;
var married = false;
var sex = ‘M’
console.log(firstname);
console.log(age);
console.log(married);
console.log(sex);
console.log(firstname+" "+lastname); // ES5
console.log(firstname,lastname); // ES5
console.log(`${firstname} ${lastname}`); // ES6
console.log(`Fullname: ${firstname} ${lastname} – (${sex}) ${age} – Married: ${married}`); // ES6
var fullname = `${firstname} ${lastname}` // ES6
console.log(fullname);
// let
var people = [‘Jon Doe’, ‘Jane Doe’, ‘Mick Doe’];
// Pollutes global namespace.
for (var i = 1; i <= people.length; i += 1) {
console.log(`person ${i} is ${people[i-1]}.`);
}
console.log(i); // 4
// Only in scope in the for
for (let j = 1; j <= people.length; j += 1) {
console.log(`person ${j} is ${people[j-1]}.`);
}
try {
console.log(j); // Reference error
} catch (err) {
console.log(`Error: ${err}.`);
}
// const
const PI = 3.142
console.log(PI);
// PI = 6; // Syntax error – PI is readonly
[/code]
Better to use let and const instead of var
Start Node and run the code
- npm start
Tag:ECMA, ES6, JavaScript, nodejs, Variables