Question

I’m using the following JavaScript. The final result is display sequence character.
But I want to display alphanumeric in-sequence order. How do I do that?

var disp = '';
var string = '';
var i;
var chars = "0123456789abcdefghiklmnopqrstuvwxyz";

var ran_unrounded;
var ran_number;
var rnum;
for (i = 0; i < 5; i++) {
    rnum = Math.floor(Math.random() * chars.length);
    string += chars.substring(rnum, rnum + 1);

    ran_unrounded = Math.random() * 3;
    ran_number = Math.floor(ran_unrounded);
    //document.write(chars.substring(rnum, rnum + 1));
    // alert('rnum', rnum, '--', rnum + 1);

    disp = chars.substring(rnum, rnum + 8);
}

Answer 1

OK, so from the clarification in the comments above the requirement is to generate a string that contains two random “words”, where each “word” has four characters selected at random from a predefined set of available characters.

Following is one way to do that:

var chars = "0123456789abcdefghiklmnopqrstuvwxyz";
function getWord(numChars) {
    var word = "",
        i;
    for (i = 0; i < numChars; i++)
        word += chars.charAt(Math.floor(Math.random() * chars.length));
    return word;
}
function getWords(numWords, numCharsPerWord) {
    var words = [],
        i;
    for (i = 0; i < numWords; i++)
        words.push(getWord(numCharsPerWord));
    return words.join(" ");
}

console.log( getWords(2, 4) );        // "a8ak 1wp9"
console.log( getWords(3, 4) );        // "7ua1 zh80 yy3r"
console.log( getWords(2, 5) );        // "j5ms2 e4xn8"

Demo: http://jsfiddle.net/dgnwh/