JS Depth 1

1.JS Data types

1.1 +-arithmetic logic

var x= "The answer is" +42; The answer is 42

var y=42+ "is the answer";//Is the answer

But

var z= "37"-7; 30

var s= "is the answer"-42; 0;

You can use the +-sign to convert the data type. string-0---> Numeric string+0---> Character type

1.2 = = Arithmetic

• "1.23" ==1.23//Converts a string to a number and compares it
• 0==false//Converts the Boolean value false to number 0 and then compares
• null==undefined//
• New Object () ==new object ()//false?
• [1,2]==[1,2]//false?

1.2.1 strictly equals = = =

First, the data types on both sides of the = = = are determined, and the type is different, returning false directly. Is the same type, the value is compared.

Null===null

undefined===undefined

Nan!=nan this NaN and any numerical comparison are unequal, and compared to their own.

1.3 Packaging Objects

JS Depth 1