What are the specific basic data types in JS development?
JSData types include basic data types, complex data types and special data types. Today we will mainly explain the basic data types of js first. Friends who are not clear about or interested in js data types, let’s take a look.
What are the basic data types in JS development? The data types of JS include basic data types, complex data types and special data types. Today we will mainly explain the basic data types first.
0. Let me first remind you of the following two knowledge points:
0.1typeof is used to detect variable types
Writing: typeof a;
0.2console.log() is used to print the part you need on the console
Generally, after entering the HTML file page, click Right-click and select Inspect, and a console will appear. Select console to see what you printed.
In addition: alert() is the page pop-up box display content
document.write() It is the way to output content on the page
1. Variables: Before talking about basic data types, let’s first understand how JSdefines variables.
1.1 Define variables: When defining a variable, you can give the variable an initial value, regardless of type (container type).
1.2 Naming specifications for variables: a combination of letters, numbers, underscores and $; cannot start with a number; cannot be keywords or reserved words; camel case naming method.
1.3 The initial value can only be the following five types:
Numeric type Number, which can only be numbers or decimals
var a = 10; console.log(typeof a);//number var b = 10.6; console.log(typeof b);//number
characters StringType String, any character wrapped in single quotes or double quotes
var c = 'hello'; console.log(typeof c);//string var d = "world"; console.log(typeof d);//string
Boolean typeBoolean, can only be true or false to represent true or false
var e = true; console.log(typeof e);//boolean var f = false; console.log(typeof f);//boolean
Undefined is undefined. No value is assigned after defining the variable. This variable is undefined
var g; console.log(typeof g);//undefined
Empty null is the object type. There are many types of object types, such as array objects, mathematical objects, and date objects (later learning)
var h = ""; console.log(typeof h);//null
These five are the five basic data types of JS.
Mutual conversion between numeric type, string type and Boolean type
2.1 Convert value—Number()
console.log(Number("123"));//123 console.log(Number("12.3"));//12.3 console.log(Number("12hshs"));//NaN console.log(Number('0034'));//34 console.log(Number(""));//0 console.log(Number(true));//1 console.log(Number(false));//0 console.log(Number(null));//0 console.log(Number(undefined));//NaN
Note: NaN: not a number, others will be explained later
2.2 Convert string String( ), convert whatever you write
console.log(String(123));//123 console.log(String(0));//0 console.log(String(true));//true console.log(String(false));//false console.log(String(undefined));//undefined console.log(String(null));//null
2.3 Convert Boolean to Boolean ()
Tips:
Convert numbers to boolean and non-0 is true
characters Convert string to boolean and non-empty to true
NaN null undefined to string to false
console.log(Boolean("123"));//true console.log(Boolean("0"));//true console.log(Boolean("山东"));//true console.log(Boolean(""));//false console.log(Boolean("true"));//true console.log(Boolean("false"));//true console.log(Boolean(14));//true console.log(Boolean(0));//false console.log(Boolean(NaN));//false console.log(Boolean(-100));//true console.log(Boolean(undefined));//false console.log(Boolean(null));//false
The above is the specific basic data types in JS development introduced by the editor. I hope to be helpful! !
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