JS -- 如何判断数组中是否有重复的元素

var sfIds = [];
for(var i=0;i<softwareInfo.length;i++){
	sfIds.push(softwareInfo[i].softwareName[2]);
}
var repeatSfIdFlag = _self.isRepeat(sfIds);
if(repeatSfIdFlag){
	_self.$message({
          showClose: true,
          message: _self.$t('tips.repeatSoftwareId'),
          type: 'error'
        });
	return;
}

isRepeat(arr){
    let  hash = {};
    for(let i in arr) {
        if(hash[arr[i]]) {
            return true;
　　     }
        hash[arr[i]] = true;
    }
    return false;
 }