How to convert JS string to number

This article mainly introduces the method of converting JS string to number. It has certain reference value. Now I share it with you. Friends in need can refer to it.

There are many ways to convert String to Number. , I can think of 5 kinds! But there are always some situations that catch people off guard. Let’s summarize them here for your convenience in the future

parseInt

According to JsPerf.com’s benchmark test, most browsers respond best to parseInt. Although it is the fastest way, using preseInt will encounter some common pitfalls: parseInt: When no base is passed in, the default is the base passed in is 10 parseInt(num, 10), if you do not know the num attribute type, do not use parseInt to convert strings to numbers.

parseInt('043') // returns 0 部分老浏览器.
parseInt('20.mp4') // returns 20

parseFloat

This is a very good choice if you don't parse hexadecimal numbers. Negative hexadecimal digits in strings are a special case, and if you parse them with parseFloat, the result will be incorrect. To avoid NaN situations in your program, you should check the converted value.

parseInt(-0xFF) // returns -255
parseInt("-0xFF") // returns -255
parseFloat(-0xFF) // returns -255
parseFloat("-0xFF") // returns 0
parseFloat('44.jpg') // return 44

Bitwise not

can convert a string into an integer, but it is not a floating point number. If it is a string conversion, it will return 0;What is the principle? By flipping) each bit, also known as the A1 complement of the number. You can use it, but note that it can only be used to store integers. So generally don't use it unless you can be sure that the number is between 32-bit integers (because of the specification of calling ToInt32). Bitwise NOT: Use this to ensure there are no characters in the input, only for integers.

~~1.23 // returns 1
~~"1.23" // returns 1
~~"23" // returns 23
~~"Hello world" // returns 0

Number

Number has the same problem as the conversion method mentioned above. When parsing, it tries to find out the number you gave it: Note: 023 is actually an octal number Number, no matter how you do it, it returns 19; the same is true for hexadecimal numbers without single or double quotes. Number is also one of the slowest in JsPerf.

Number("023") // returns 23
Number(023) // returns 19

Unary cloud operator

"1.23" * 1 // returns 1.23
"0xFF" - 0 // returns 255
"0xFF.jpg" / 1 // returns NaN
+"023" // returns 23

The unary operator is different from other parsing methods. If it is a NaN value, then the returned value is also NaN. This is my favorite way to convert numeric values, because I don't think any object with characters should be treated as 0 or "guessed" based on how many bits it has. I basically use the operator because this method is less confusing. Although the usage of -0 is also good, it does not express the original intention of converting to a number very well.

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