preface

Today is a sunny day, is looking for new material, see awesome group friends put forward a question is



why'1' < '10' == true 而 '2' < '10' == false?

imagine

‘1’ < ’10’ == true But it makes sense here! Please listen to me slowly

First declare a point if other types of the same type really do not cast to compare.

  • However, if a String is of the same type, it will be converted to Unicode code alignment.
  • And the default conversion is the first character of Unicode code, if equal will be compared one by one, until the result is produced, will stop the comparison and return the result

Converting to code is:

 '1'.charCodeAt() < '1'.charCodeAt() // Compare string 1 to Unicode code with string 1 to Unicode code
 ' ' < '0'.charCodeAt() 
Copy the code

They compare the first ☝️ and get the same Unicode code, and then compare the second but ‘1’ has only one digit, so they get the Unicode code for ” and ‘0

That’s it, by the rule that null characters and numbers are strongly converted to numbers

Empty objects are converted to 0



So you get the result'1'< '10' == trueSet up!

The transformation rules are detailed:

‘0’ < “special contrast



In fact, there are special judgments like'0' < 'That’s because the null character passes throughUnicode codeisNaN 而'0'Is 48Unicode code

NaNIt’s not legally specialNumberValue and greater than the legal array, exceptInfinityinfinity

conclusion

Understanding this concept is a good way to explain why ‘1’ < ’10’ is that they are not different types of comparison, and not == comparison, size comparison will convert their first character to Unicode code size, if the first character comparison is the same unicode code will be compared one by one.

Extend the example

  • The first one is because there’s anumberSo it’s converted to numberTo compare
  • The second one is bothstringAnd the size is converted to the first letter of the contrastUnicode codeContrast. After equivalent to' ' 和 Unicode codeThe contrast of

Here’s another fun one

This is because the Unicode code for ‘select’ is larger than the Unicode code for ‘nu’

It also proves that every choice you make matters. Work together and make progress together. I’m Ah Jiang!