Just to find the number of occurences:
1) var regExp = new RegExp(value, "gi");
return (str.match(regExp) || []).length;
2) Most Efficient:
var n=0, pos=0;
var subStr = 'dolor';
var subStrLength = (subStr)?subStr.length:0;
while(true){
pos = str.indexOf(subStr,pos);
if(pos>-1){
n++;
pos += subStrLength;
} else {
break;
}
}
console.log(n);