convert uppercase and lowercase in javascript [duplicate]

问题

I want to make a code that converts uppercase and lowercase in Javascript.

For example, 'Hi, Stack Overflow.' ----> 'hI, sTACK oVERFLOW'

How can I do it?

回答1:

You could run over each character, and then covert it to lowercase if it's in uppercase, to uppercase if it's in lowercase or take it as is if it's neither (if it's a comma, colon, etc):

str = 'Hi, Stack Overflow.';
res = '';
for (var i = 0; i < str.length; ++i) {
    c = str[i];
  if (c == c.toUpperCase()) {
    res += c.toLowerCase();
  } else if (c == c.toLowerCase()) {
    res += c.toUpperCase();
  } else {
    res += c;
  }
}

回答2:

You can try this simple solution using map()

var a = 'Hi, Stack Overflow!'

var ans = a.split('').map(function(c){
  return c === c.toUpperCase()
  ? c.toLowerCase()
  : c.toUpperCase()
}).join('')

console.log(ans)

回答3:

<!DOCTYPE html>
<html>
<head>
<title>hello</title>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.4/jquery.min.js"></script>
</head>
<body>

<script>
$(document).ready(function(){
    var x = 'Hi, Stack Overflow.';

    alert(caseAlter(x));

    function caseAlter(txt){
        var output = "";

        for(var i = 0; i < txt.length; i++){
            if(txt[i] == txt[i].toUpperCase()){
                output += txt[i].toLowerCase();
            }else{
                output += txt[i].toUpperCase();
            }           
        }

        return output;
    }

});
</script>
</body>
</html>

回答4:

var hi = 'Hi, Stack Overflow.';

var hI = hi.split("");
for(var i=0;i<hI.length;i++){
if(hI[i] == hI[i].toLowerCase())hI[i]  = hI[i].toUpperCase();
else if(hI[i] == hI[i].toUpperCase())hI[i] = hI[i].toLowerCase();
} 
hI = hI.join("");
alert(hI);
//'hI, sTACK oVERFLOW'

回答5:

var input = 'Hi, Stack Overflow.'
var arr = input.split(' ');

alert(arr);
var output = arr.map(function(elem){

  return (elem[0].toLowerCase() + elem.substring(1,elem.length).toUpperCase());

});

alert(output.join());

回答6:

A function which will do this for you:

function reverseCase(input) {
    var output = []
    for(var char in input) {
        var character = input[char]
        if(character == character.toUpperCase())
            output.push(character.toLowerCase())
        else
            output.push(character.toUpperCase())
    }
    return output.join('')
}

来源：https://stackoverflow.com/questions/40192262/convert-uppercase-and-lowercase-in-javascript

标签

javascript

string

uppercase

lowercase