Remove duplicated characters from string

removeDuplicates.js

/*
    Example input => output
    aaaaaaaaaaaaaaaabc => abc
    aaaaabbbac => abac
*/
function removeDuplicates(str) {
	if(str === null || str === undefined) {
		return null
	}

	if(str.length <= 1) {
		return str;
	}

	var result = [];
	result.push(str[0]);
	for (var i = 1; i < str.length; i++) {
		if(result[result.length-1] !== str[i]) {
			result.push(str[i]);
		}
	};

	return result.join('');
}