20、多个数组求交集

[shengq666]

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[shengq666]

1、合并数组 循环判断数组中的值出现的次数

function ar() {
    let args = [...arguments]
    let tmpArr = []
    let returnArr = []
    for(let i=0;i<args.length;i++) {
        tmpArr = [...tmpArr,...args[i]]
    }
    for(let i=0;i<tmpArr.length;i++) {
        let count = 0
        for(let j=0;j<tmpArr.length;j++) {
            if(tmpArr[i] === tmpArr[j]) {
                count++
            }
            if(count === args.length && returnArr.indexOf(tmpArr[i])<0 ) {
              returnArr.push(tmpArr[i])  
               break
            }
        }
    }
    return returnArr
}

2、reduce 结合 filter，累加后的数组对当前项进行过滤

function intersect() {
    let args = [...arguments]
    if(args.length === 0) {
        return []
    }
    if(args.length === 1) {
        return args[0]
    }
    return args.reduce((accu,curr)=>{
        return accu.filter(v => curr.indexOf(v) > -1);
    })
}