This article brings you what are the return data types of typeof in js? The summary of js typeof return type and type conversion has certain reference value. Friends in need can refer to it. I hope it will be helpful to you.
js typeof has six return types:
undefined, string, boolean, number, symbol (ES6), Object, Function.
Note: There is no array array. If it is an array, object will be returned.
Forced type conversion of js
js provides two conversion functions: parseInt() and parseFloat(). The former converts the value to an integer, and the latter converts the value to a floating point number. Only by calling these methods on the String type can these two functions run correctly; for other types, NaN (Not a Number) is returned.
parseInt()
parseInt("1234blue"); //returns 1234 parseInt("0xA"); //returns 10 parseInt("22.5"); //returns 22 parseInt("blue"); //returns NaN
parseInt() method also has base mode, which can convert binary, octal, hexadecimal or any other base Convert string to integer. The base is specified by the second parameter of the parseInt() method, as shown in the following example:
parseInt("AF", 16); //returns 175 parseInt("10", 2); //returns 2 parseInt("10", 8); //returns 8 parseInt("10", 10); //returns 10
If the decimal number contains leading 0s, it is best to use base 10 so that you do not accidentally get an octal value. For example:
parseInt("010"); //returns 8 parseInt("010", 8); //returns 8 parseInt("010", 10); //returns 10
parseFloat()
Another difference in using the parseFloat() method is that the string must represent a floating point number in decimal form, and parseFloat() has no base mode .
parseFloat("1234blue"); //returns 1234.0 parseFloat("0xA"); //returns NaN parseFloat("22.5"); //returns 22.5 parseFloat("22.34.5"); //returns 22.34 parseFloat("0908"); //returns 908 parseFloat("blue"); //returns NaN
Boolean(value)——Convert the given value into Boolean type;
Boolean(""); //false – empty string Boolean("hi"); //true – non-empty string Boolean(100); //true – non-zero number Boolean(null); //false - null Boolean(0); //false - zero Boolean(new Object()); //true – object
Number(value)——Convert the given value to Convert a given value into a number (can be an integer or a floating point number);
Number(false) 0 Number(true) 1 Number(undefined) NaN Number(null) 0 Number( "5.5 ") 5.5 Number( "56 ") 56 Number( "5.6.7 ") NaN Number(new Object()) NaN Number(100) 100
String(value)——Convert the given value into a string.
var s1 = String(null); //"null" var oNull = null; var s2 = oNull.toString(); //won't work, causes an error
Using js variable weak type conversion
<script> var str= '012.345 '; var x = str-0; x = x*1; </script>
The above example takes advantage of the weak type characteristics of js and only performs arithmetic operations to achieve string to number conversion. Type conversion, but this method is still not recommended.
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