How to determine whether it is a string in javascript

Javascript method to determine whether it is a string: first use the typeof operator to return the type of the uncalculated operand; then use the constructor attribute to return a reference to the Boolean function that created this object; finally pass "== "Just determine whether the two return values ​​​​are strings.

The operating environment of this tutorial: windows7 system, javascript version 1.8.5, Dell G3 computer.

javascript determines whether it is a string type

var str="123";
if((typeof str=='string')&&str.constructor==String){
	console.log("str是字符串类型");
}

Output:

str是字符串类型

[Recommended learning: js basic tutorial】

Description:

1. typeof operator:

typeof operator returns a string, indicating uncalculated The type of operand.

The syntax is as follows (typeof operator followed by operand):

typeof operandtypeof(operand)

Parameters:

• operand: a representation object or primitive value The expression whose type will be returned.

2. Constructor attribute:

The constructor attribute returns a reference to the Boolean function that created this object.

Grammar:

object.constructor

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