var genArray = (function() {
	var length = 5,
		range = [-100, 100];

	function getRandomInt() {
		return Math.floor(Math.random() * (range[1] - range[0] + 1)) + range[0];
	}
  
	return function() {
		var n, result = [];
    
		while(result.length < length) {
			n = getRandomInt();
			if(result.indexOf(n) === -1) {
				result.push(n);
			}
		}
    
		return result;
	}
})();

<button onclick="alert(genArray())">CLICK</button>

<button>Создать</button>
<script>
var rnd =()=> Math.floor(Math.random() * (100 + 100)) + -100;
document.querySelector('button').onclick = e =>{
var arr = [];
for (var i =0; i<5; i++)  arr.push(rnd());
	console.log(arr);
};
</script>