Today #day45 of #100daysofcode, I have completed 8.55 & 8.56 lessons and a "London is the capital of GB" code practice problem in the JS course. @Sololearn
ECMAScript 6
What is ECMA?
European Computer Manufacturers Association (ECMA).
ECMA is a standard, and Javascript and Jscript are an implementation of those standards.
Intro to ES6
ECMAScript (ES) is a scripting language specification created to standardize JavaScript.
ES6 - 2015
ES13 - June 2022
ES6 variables and strings
3 Ways of declaring a variable in ES6
var a = 10;
const b = 'hello';
let c = true;
The type of declaration used depends on the necessary scope.
The scope is the fundamental concept in all programming languages that defines the visibility of a variable.
var type declaration
var keyword, which defines a variable globally, or locally to an entire function regardless of block scope.
var -> variable
you can reassign where type declare declaration.
let type declaration
let allows you to declare variables that are limited in scope to the block, statement, or expression in which they are used.
The best use for let is in loops.
let is not subject to Variable Hoisting, which means that let declarations do not move to the top of the current execution context.
You can reassign a let type declared declaration.
const type declaration
const variables have the same scope as variables declared using let.
The difference is that const variables are immutable i.e they are not allowed to be reassigned.
const is not subject to Variable Hoisting too, which means that const declarations do not move to the top of the current execution context.
Note:
- Also, note that ES6 code will run only in browsers that support it. Older devices and browsers that do not support ES6 will return a syntax error.
Summary:
"var" is for globlal scope.
"let" is for block scope.
"const" is for block scope and value of it unchangeable
Template Literals in ES6
- Template literals are a way to output variables in the string.
Before ES6 we had to break the string. For example,
let name='spiderman'
let log = 'friendly neighbourhood' + name + '!'
console.log(log)
- ES6 introduces a new way of outputting variable values in strings.
The same code above can be rewritten as:
let name='spiderman'
let log = `friendly neighbourhood' ${name} '!'`
console.log(log)
Observe, that template literals are encapsulated by the backtick (` `) character instead of double or single quotes(like in ES5).
The ${expression} is a placeholder, and can include any expression, which will get evaluated and inserted into the template literal.
Note:
- To escape a backtick in a template literal, put a backslash
\before the backtick.
Images
8.55 & 8.56 completed
Conclusion
ECMAScript 6
What is ECMA?
Intro to ES6
ES6 variables and strings
3 Ways of declaring a variable in ES6
Template Literals in ES6
My Code:
London is the capital of GB
