Generate unique color code based on string input [JS]

gen_color.js

var stringToColour = function(str) {
    var hash = 0;
    for (var i = 0; i < str.length; i++) {
        hash = str.charCodeAt(i) + ((hash << 5) - hash);
    }
    var colour = '#';
    for (var i = 0; i < 3; i++) {
        var value = (hash >> (i * 8)) & 0xFF;
        colour += ('00' + value.toString(16)).substr(-2);
    }
    return colour;
}

var text = prompt("Please enter text");

document.write(stringToColour(text))
$('body').css('background-color', stringToColour(text));