js 根据权重概率随机

//数组元素叠加 [1,2,3,4,,] -> [1,3,6,10,,,,]
function arrOverAdd(arr){
    if( !arr || arr.length <= 0){
        return [];
    } else {
        var temp = [];
        for(var i = 0;i < arr.length ; i++){
            if(i == 0){
                temp[i] = parseInt(arr[i]);
            } else {
                temp[i] = temp[i-1] + parseInt(arr[i]);
            }
        }
        return temp;
    }
}


/**
 * 获取数组中最接近的值得index
 * @param random 随机数
 * @param weightArray 权重数组
 * @returns {number}
 */
function getArrIndex(random,weightArray){
    var index = 0;
    if(random <= weightArray[0]){
        return 0;
    } else if(random >= weightArray[weightArray.length-1]){
        index = weightArray.length - 1;
        return index;
    } else {
        for(var i = 0 ;i < weightArray.length; i++){
            if(random <= weightArray[i]){
                index = i;
            } else if(random > weightArray[i] && random <= weightArray[i + 1]){
                index = i + 1;
                break
            } else if (random > weightArray[i] && random <= weightArray[ i + 1] ){
                index = i + 1;
                break;
            }
        }
    }
    return index;
}


var weightArr = [10,20,30,30,10];

weightArr = arrOverAdd(weightArr);
console.log(weightArr);
var totalWeight = weightArr[weightArr.length - 1];

var random = Math.random() * totalWeight;
console.log(random);
var arrIndex = getArrIndex(random,weightArr);
console.log(“索引：”+arrIndex);