I'm trying to write a function that takes the string and changes all the lowercase letters to uppercase and vice versa. "lower UPPER" would translate to "LOWER upper"

Heres what I have:

var convertString = function (str){
var s = '';
var i = 0;
while (i < str.length) {
    var n = str.charAt(i);
        if (n == n.toUpperCase()) {
            n = n.toLowerCase;
        }
        else {
            n = n.toUpperCase;
        }

 i +=1; 
 s += n;

}
return s;
};
convertString("lower UPPER");

I'm using this website to work and am getting a pretty weird message outputted.

Here is a pic of what happens after I run it.

I'm trying to write a function that takes the string and changes all the lowercase letters to uppercase and vice versa. "lower UPPER" would translate to "LOWER upper"

Heres what I have:

var convertString = function (str){
var s = '';
var i = 0;
while (i < str.length) {
    var n = str.charAt(i);
        if (n == n.toUpperCase()) {
            n = n.toLowerCase;
        }
        else {
            n = n.toUpperCase;
        }

 i +=1; 
 s += n;

}
return s;
};
convertString("lower UPPER");

I'm using this website to work and am getting a pretty weird message outputted.

Here is a pic of what happens after I run it.

• javascript
• string

• 1 'lower UPPER'.replace(/./g, c => c === c.toUpperCase() ? c.toLowerCase() : c.toUpperCase()) – zerkms Commented Jan 27, 2016 at 4:07

2 Answers 2

You have just about everything correct, except for inside of your if statement. You're setting n equal to its toLowerCase or toUpperCase method, not its return value. You need to call those methods and set n equal to their return values:

var convertString = function (str) {
    var s = '';
    var i = 0;
    while (i < str.length) {
        var n = str.charAt(i);
        if (n == n.toUpperCase()) {
            // *Call* toLowerCase
            n = n.toLowerCase();
        } else {
            // *Call* toUpperCase
            n = n.toUpperCase();
        }

        i += 1;
        s += n; 
    }
    return s;
};

convertString("lower UPPER");

The output that you're getting ('function toUpperCase() { [native code] }...) is the result of each method being converted to a string, then concatenated to your result string. You can achieve the same result by running either of these mands in your console:

• console.log("".toUpperCase);
• console.log("".toUpperCase.toString());

The results of both are function toUpperCase() { [native code] }.

Happy coding!

Use ES6 Syntax:

You could use ES6 features JavaScript has to offer which would reduce the source code:

const convertString = str => [...str].map(char => char === char.toUpperCase() ? char.toLowerCase() : char.toUpperCase()).join('');

console.log(convertString("lower UPPER"));