数组操作

判断一个元素是否在数组中

export const contains = (arr, val) => {
    return arr.indexOf(val) != -1 ? true : false;
}

数组排序，{type} 1：从小到大 2：从大到小 3：随机

export const sort = (arr, type = 1) => {
    return arr.sort((a, b) => {
        switch (type) {
            case 1:
                return a - b;
            case 2:
                return b - a;
            case 3:
                return Math.random() - 0.5;
            default:
                return arr;
        }
    })
}

去重

export const unique = (arr) => {
    if (Array.hasOwnProperty('from')) {
        return Array.from(new Set(arr));
    } else {
        var n = {}, r = [];
        for (var i = 0; i < arr.length; i++) {
            if (!n[arr[i]]) {
                n[arr[i]] = true;
                r.push(arr[i]);
            }
        }
        return r;
    }
}

求两个集合的并集

export const union = (a, b) => {
    var newArr = a.concat(b);
    return this.unique(newArr);
}

求两个集合的交集

export const remove = (arr, ele) => {
    var index = arr.indexOf(ele);
    if (index > -1) {
        arr.splice(index, 1);
    }
    return arr;
}

删除其中一个元素

export const remove = (arr, ele) => {
    var index = arr.indexOf(ele);
    if (index > -1) {
        arr.splice(index, 1);
    }
    return arr;
}

将类数组转换为数组

export const formArray = (ary) => {
    var arr = [];
    if (Array.isArray(ary)) {
        arr = ary;
    } else {
        arr = Array.prototype.slice.call(ary);
    };
    return arr;
}

最大值

export const max = (arr) => {
    return Math.max.apply(null, arr);
}

最小值

export const min = (arr) => {
    return Math.min.apply(null, arr);
}

求和

export const sum = (arr) => {
    return arr.reduce((pre, cur) => {
        return pre + cur
    })
}

平均值

export const average = (arr) => {
    return this.sum(arr) / arr.length
}

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