思路：

function findAllOccurrences(arr, target) {
    var a=[]
    for(var i =0;i<arr.length;i++){
        if(arr[i]==target){
            a.push(i);
        }
    }
    return a;
}

function findAllOccurrences(arr, target) {
    var temp=[];
    arr.forEach(function(val,index){
        if (val===target)
        {
            temp.push(index);
        }
    });
    return temp;
}