JS type conversion

First, JS data type

Raw data type: Null number String Undefined Boolean symbol (denotes unique value) about Symbol https://www.jianshu.com/p/174f88d189c6

Reference type Object

Second, type conversion

1.Number function

• Original type

1. String: Converts to a number if it can be resolved to a number, otherwise Nan, an empty string is converted to 0
2. Boolean value: True to convert to 1,false to 0
3. null:0
4. Undefined:nan

• Reference type: Object

The valueof method is called first, and if the method returns data of the original type, the number conversion is called directly;

If the ValueOf method returns a value of the reference type and then calls the object's ToString method, if the ToString method returns the data of the original type, then the number is converted;

If the ToString method returns a reference type, an error occurs.

2.String function

• Original type

1. Value: A string converted to a response
2. Boolean: True converts to "true", false to "false"
3. Null: Converted to "null"
4. Undefined: "Undefined"

• Reference type: Object

The ToString method is called first, and if the method returns data of the original type, the string conversion is called directly;

If the ToString method returns a value of a reference type, then the ValueOf method is called, and if the ValueOf method returns the data of the original type, then the string is converted;

If the ValueOf method returns a reference type, an error occurs.

3.Boolean function

Undefined null-0 +0 "(empty string) NaN is converted to false, the rest is true

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JS type conversion