JavaScript changes the case of a string

There are 4 methods in JavaScript that involve a string case conversion: toLowerCase (), toLocaleLowerCase (), toUpperCase (), and toLocaleUpperCase (). Today we will mainly use the following touppercase () and toLowerCase () methods.

JavaScript provides two ways to convert a string to all uppercase or lowercase, so that you can change "hello" to "hello" or "not" to "not". You might ask, why? Converts letters in a string to the same case, which makes it easier to compare two strings. For example, suppose you create a problem program, and a question is "who is the" the American to win the Tour De France? You may use code similar to the following to check the answers to the respondents:

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var correctanswer= ' Greg LeMond '; var response=prompt (' Who is ' the ' the ' the ' the ' the ' American to win the Tour De8? ', '); if (France Onse==correctanswer) {//correct}else{//incorrect}

The answer is Greg LeMond, but what happens if the person who participates in the answer enters Greg LeMond? The conditions look something like this: ' greg LeMond ' = ' Greg LeMond '. Because JavaScript is case-sensitive, the lowercase letter ' m ' in LeMond does not match the ' m ' in LeMond, so the participant may get the wrong answer. If the participant presses the CAPS key and enters Greg LeMond, the result will be the same.

To solve this dilemma, we can convert two strings to the same case, and then compare them:

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if (Response.touppercase () ==correctanswer.touppercase ()) {//correct}else{//incorrect}

In this case, the conditional statement converts the answer of the participant and the correct answer to uppercase letters, so ' Greg LeMond ' became ' Greg LeMond ' and ' Greg LeMond ' became ' Greg LeMond '.

To get all lowercase strings, use the toLowerCase () method as follows:

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1 2	var answer= ' Greg LeMond '; alert (Answer.tolowercase ());//' Greg LeMond '

Note that none of these methods really changes the strings that are actually stored in the variable, and they simply return the string in all uppercase or lowercase letters. So, in the example above, even after the hint appears, answer still contains ' Greg LeMond ' (They return some other value).

toLowerCase () and toUpperCase () are two classical methods that draw on the same method from Java.lang.String. The toLocaleLowerCase () and Tolocaleupper () methods are for specific locale implementations. For some regions, the approach to the region is the same as the common method, but a few languages apply special rules for Unicode case conversions, and a locale-specific approach is required to ensure that the correct transformations are implemented.

Here are a few examples:

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var sv= "Hello World"; Alert (Sv.tolocaleuppercase ());//"Hello World" alert (Sv.touppercase ());//"Hello World" alert (sv.tolocalelowercase) //"Hello World" alert (Sv.tolowercase ());//"Hello World"

The above code uses toLocaleUpperCase () and toUpperCase () to return to "Hello World", just as the call to toLocaleLowerCase () and toLowerCase () all return to "Hello World" The same. In general, it is safer to use the area-specific approach without knowing that your code will run in that language.

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