JavaScript Functions, Arrays, and JSON
Hello!
Today, I'm gonna teach you how to use some JavaScript functions. So, let
's get into it!
- Just don't use any of my bad styling, use Coder100's styling tutorial.
Variables
You've probably used var before, if you've used JavaScript. Variables in JavaScript look like this:
var foo = 'bar'; console.log(foo); // Displays bar in the console
Or this (JSON)
var fooObj = {"foo": "bar"} console.log(fooObj.foo); // Displays bar in the console again
But, most developers say not to use var
, unless you need to. So, use const
and let
as much as possible. Here is the difference.
// let { var foo = 'bar'; } console.log(foo); // Displays bar { let bar = 'foo'; console.log(bar); // Displays foo } console.log(bar) // bar is not defined
// const const foo = 'bar'; console.log(foo); // bar const foo = 'not foo'; // SyntaxError: Identifier 'foo' has already been declared
String
All string functions explained in one code block
var x = 'The terms foobar, foo, bar, and others are used as metasyntactic variables and placeholder names in computer programming or computer-related documentation. '; var y = 'They have been used to name entities such as variables, functions, and commands whose exact identity is unimportant and serve only to demonstrate a concept.'; console.log(x.charAt(0)); // "T" as in "The terms foobar, foo, bar..." console.log(x.concat(y)) // var x joined to var y console.log(x.indexOf('f')); // 10 because the first "f" is in the 10th place console.log(x.replace('The', 'Da')); // "Da terms foobar, foo, bar..." console.log(x.substring(9, 16)); // "foobar" console.log(x.toLowerCase()); // "the terms foobar, foo, bar..." Great for making things not case sensitive console.log(x.toUpperCase()); // "THE TERMS FOOBAR, FOO, BAR..."
Array
Arrays are pretty much lists. Here's how you create one and use it:
var array = [ 'foo', 'bar', 'foobar' ]; console.log(array); // ['foo', 'bar', 'foobar'] console.log(array[0]); // foo console.log(array[1]); // bar console.log(array[2]); // foobar array.pop(); console.log(array); // ['foo', 'bar'] array.push('foobar'); // ['foo', 'bar', 'foobar'] console.log(array); array.shift(); console.log(array); // ['bar', 'foobar'] array.unshift('foo'); // ['foo', 'bar', 'foobar']
JSON
JSON stands for JavaScript Object Notation. Here's a code block that explains it:
var obj = { "foo": "Bar", "fName": "Bobby", "lName": "Sue" } console.log(`${obj.foo} v1.0.0`); // Bar v1.0.0 console.log(`Your first name is ${obj.fName}`); // Your first name is Bobby console.log(`Your last name is ${obj.lName}`); // Your last name is Sue // Or, use a string. var objStr = `{ "foo": "Bar", "fName": "Bobby", "lName": "Sue" }` console.log(`${JSON.parse(objStr).foo} v1.0.0`); // Bar v1.0.0 console.log(`Your first name is ${JSON.parse(objStr).fName}`); // Your first name is Bobby console.log(`Your last name is ${JSON.parse(objStr).lName}`); // Your last name is Sue
And that's it!
Tell me in the comments if I missed anything or if there's any errors!
I like var better so no.