var list = [1, 2, 3, 4, 5, 6, 7, 8]
    var index = list.map(item => item).indexOf(8)
    console.log(index) //7

    var array = [{
        name: "aa"
    }, {
        name: "bb"
    }, {
        name: "cc"
    }, {
        name: "dd"
    }, {
        name: "ee"
    }]
    var line= array.map(item => item.name).indexOf(‘dd‘)
    console.log(line) //3