JavaScript variable type

Number Type

The number type represents a numeric type, including integral and floating-point types. JS in the long shape, short integer, single-precision, double-precision.

Number definition

The number type is defined as follows, the first of which is most commonly used. The latter two are generally not used.

var1;varnewNumber();  //初始值为0varnewNumber(1);

Number types are integral and floating-point

var1;    //整型var2.3;  //浮点

Infinity

• is a numeric type
• Represents a value that exceeds the JavaScript processing range
• Any divisor divided by 0, also infinity

//在谷歌控制台中输入typeofInfinity"number"//--------------------------var6/0Infinity//但是直接使用 typeof 6/0 最后的结果是NaNtypeof6/0NaN

NaN

• is also a numeric type
• If the calculation fails, the result is Nan
• Contagious, if there is a nan in the arithmetic operation, it causes the whole arithmetic to fail

//在谷歌控制台中输入typeofNaN"number"//--------------------------var6‘s‘NaN

typeof operator and typeof () function

typeof is used to determine the type of variable, usage:

var0vartypeof s;if(typeof‘number‘);typeof(s)

Here you only understand the usage of typeof

Note:
typeof is an operator and not a function, and typeof () is a function.

Undefined and null

Typically, when we access an unassigned variable, we get a undefined value.
Null means null and nothing.

JavaScript variable type