What types of conversions does JavaScript have?

JavaScript type conversions include: 1. To convert to a string, use ".toString", String or "num """; 2. To convert to a numeric type, use Number, parseInt or parseFloat; 3. To convert to a Boolean value, use Boolean or "!!".

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

1. Convert to string: Use .toString or String.

1, .toString() method: Note that null and underfined cannot be converted

//转为字符串-->toString方法
var bool=true;
console.log(bool.toString());
//注意，toString不能转null和underfined.

2, String() method: both can Conversion

console.log(String(null));

3. Implicit conversion: num "", when one operator on both sides is a string type and one operator is another type, the other type will be converted into a string first and then the string Splice, return string

var a=true;
var str= a+"";
console.log('str');

2. Convert to numerical type

1, Number(): Number() can convert any value into a numerical value. If there is a character that is not a numerical value in the string to be converted, NaN

console.log(Number(true));

2, parseInt():

var a="12.3px";
console.log(parseInt(a);
//结果：12.3.  如果第一个字符是数字会解析知道遇到非数字结束.
var a="abc2.3";
console.log(parseInt(a);
结果：返回NaN，如果第一个字符不是数字或者符号就返回NaN.

3, is returned. parseFloat(): parseFloat() converts a string into a floating point number, parseFloat() is very similar to parseInt, the difference is that parseFloat will parse the first one. The second one is encountered. Or end with non-number. If the parsed content contains only integers, parse it into integers.

4. Implicit conversion:

var str="123";
var num=str-0;
console.log(num);
//结果为数值型；

3. Conversion to Boolean(): 0 '' (empty string) null undefined NaN will be converted to false and others will be converted to true

Method:

1, Boolean():

console.log(Boolean(2));

2,

var message;
if(message){};

3, Implicit conversion: ! !

var str="123";
var bool=!!str;
console.log(str);

【Recommended learning: javascript advanced tutorial】

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