我最近开始学习一门课程，并且对JavaScript还是很陌生。我正在执行一项任务，要求我找到我的设备达到两次的第一个频率。给我989个数字，从正数到负数不等，我必须找出哪个数字首先显示为倍频。例如：+ 3，+ 3，+ 4，-2，-4首先到达10两次。
我尝试了不同的代码变体，但是没有一个给我输出，好像由于大量数字而中断了输出。我需要输入的所有数字的pastebin可以在这里找到：https://pastebin.com/VESwwM2y使用这些数字，我必须找出哪个数字先出现两次。这是我一直在使用的代码：
function find_duplicate_in_array(arra1) {
var object = {};
var result = [];
arra1.forEach(function (item) {
if(!object[item])
object[item] = 0;
object[item] += 1;
})
for (var prop in object) {
if(object[prop] >= 2) {
result.push(prop);
}
}
return result;
}
console.log(find_duplicate_in_array([]));
我只需要弄清楚如何使它工作。
答案 0 :(得分：0)
一旦发现第一个重复项，就可以使用Array#some并停止循环执行
var array = [+4, +3, -15, -8, +15, -17, -16, +15, -10, +1, +17, +19, -10, +17, +11, +3, -13];
function getFirstDuplicate(arr) {
var obj = {}, duplicate;
arr.some(function(item) {
if (!obj[item]) {
obj[item] = 1;
return false;
} else {
duplicate = item;
return true;
}
});
return duplicate;
}
console.log(getFirstDuplicate(array))
答案 1 :(得分：-1)
这应该为您提供工具
let arr = [];
let res = [];
const searchIt = (num,i) => {
const n=arr.indexOf(num);
if (n!==-1) {
if (res.indexOf(num) ==-1) res.push(num);
console.log(num,"@pos",i," found at ",n);
}
arr.push(num);
}
`+4
+3
-15
-8
+15
-17
-16
+15
-10
+1
+17
+19
-10
+17
+11
+3
-13
-13
-20
+10
-7
+2
-12
+2
+2
+7
+7
+19
-18
-10
+16
+18
-9
+15
-16
+15
+15
+14
+13
+15
+2
+6
+10
+12
+13
+8
+3
-19
-12
+19
+13
+4
+16
+16
-10
+15
-16
+17
+16
+5
+1
+17
+15
-16
+3
+17
-9
-4
-11
+2
+19
-12
+9
+8
+8
-7
+17
-15
-17
+18
+9
-11
+10
+5
-18
+15
+12
-3
-2
+18
-1
+5
+12
+3
-7
+16
+3
+4
+17
-13
+7
-13
+3
+7
+13
+4
-10
-13
+4
+13
+15
+14
-13
+10
-9
-16
+4
+18
-13
-11
+13
+8
-11
+18
+19
-16
-6
-5
+16
-10
-14
+7
+10
+10
-16
-19
+10
-5
+13
+24
-1
+9
+2
+12
+11
-4
-17
+2
-17
+8
+18
-10
+2
-6
-2
-12
+21
+16
-21
-7
-6
-7
-3
+14
+16
+3
+10
-14
+2
+15
+9
+13
+4
+2
-9
-9
+4
-2
-11
-9
+16
+9
-6
-17
+22
+8
+16
+5
+9
+18
-5
-1
+13
-8
-11
+10
+6
+9
-1
+13
+11
-3
-12
+17
-19
-11
+10
+17
+15
+9
+9
+4
-3
+9
-4
+8
-7
+12
+5
-2
-6
-17
+12
+18
+14
-1
+15
+12
-19
-16
-4
-4
+1
-9
+5
-6
+4
+16
-1
+18
+5
+17
-1
+5
+15
+4
+3
-11
+5
+18
-3
+2
+7
-13
+10
+21
-7
+6
-2
-20
-11
-12
-18
-7
-15
+9
-1
+18
-10
-5
-15
+3
-20
+22
-18
+11
-6
+15
-16
+17
+6
+20
+19
-8
-21
-8
+9
+21
-15
+10
+17
+16
-22
+5
+5
-20
+7
+22
-1
+11
-17
-14
-15
+2
-8
+11
-4
-37
-9
-10
+30
+8
+50
+28
-10
+6
+16
+2
+11
+8
+14
-17
-11
+18
+1
+1
-3
+17
+15
-1
+13
+9
-20
-7
+20
+18
-16
-12
+19
+2
+10
-13
-4
-12
+2
-11
-15
-1
+22
-12
-4
+1
-12
-9
-1
+17
+15
-6
-12
-16
-5
+16
+20
-18
-5
-17
-1
-12
+21
-13
-5
+15
+36
-12
+5
+30
+48
-7
+2
+7
+10
-14
+11
-17
+34
+20
+17
-16
-4
-7
-6
+1
+11
+11
+5
-14
+35
+16
+6
+28
-3
+18
-4
-6
-12
-13
+30
+12
+16
-14
-15
+14
-6
+17
+2
+10
-15
-19
-20
+22
-20
+12
-8
+9
-19
+40
+17
-1
+3
+7
+12
-26
-3
-5
-5
+12
+24
-10
+3
-27
+6
+13
-23
+5
-27
-41
-5
-41
+144
-40
+155
+29
-26
+16
+9
-229
-70
+401
+64265
-10
+19
-3
-14
+10
+2
+13
+13
-19
-18
-11
+16
-19
+10
-2
-7
-12
-13
-16
+19
-12
+14
+2
+15
+17
+14
+19
+8
+14
-7
-16
+11
+15
+9
+11
+5
-8
+16
-11
-16
-14
+10
-13
-13
+8
-3
-23
-19
-18
-3
-7
+18
+5
-2
+13
+10
-8
-16
+22
-9
+18
+7
+22
-3
-17
+11
+11
+12
+11
+7
+16
+12
+2
-16
-8
+15
+8
-4
+2
-4
+12
-18
+15
-17
-20
+18
-1
+6
-22
+23
+19
+3
+15
-17
-2
+7
+1
-12
-7
-15
-4
+15
-13
+11
+14
+16
+19
+7
-3
-10
+12
-22
+6
-2
-14
+18
-1
+27
+13
+15
+10
+18
+10
+11
-13
+11
-1
+7
+3
-2
+14
-8
-2
+9
-16
+13
+7
+19
-15
+3
+9
+14
-8
+13
+19
-10
-6
-4
+7
+6
-1
-6
-4
-16
+1
+18
+17
+1
+16
+17
-19
+12
+21
+10
+7
+3
-9
-9
+11
+17
+5
+13
+2
+15
-6
-18
+14
+17
-2
-12
-14
+1
-18
-1
-12
-13
+7
+14
+14
-18
+1
+19
-9
-17
-15
-14
-12
-20
+12
-8
+1
+8
+11
+6
+8
+10
-9
-6
+20
+5
+14
-17
-13
+22
+13
+3
+11
+19
-1
-9
-5
-22
+19
+20
-16
+6
+15
-2
+31
+12
+3
+4
+24
+16
-6
+11
-20
+18
+8
-9
-9
+28
-4
-3
-17
-9
-11
-1
+15
+13
+12
-30
-16
+19
-22
+2
-18
+7
-8
-24
+31
+5
+36
+3
+48
+10
+19
-7
-11
+5
+3
+7
+4
-15
+13
+10
-7
+14
+9
+7
+11
+12
-3
+6
-17
+7
-15
-10
+17
-4
-17
-13
+18
-3
-9
+5
+10
-12
-1
+15
+20
-3
-1
-1
-6
+15
-2
+13
+19
-1
+8
+17
+4
+1
+18
+1
+4
+12
+3
-5
-21
-15
-14
+20
+5
+18
-6
-5
-5
+4
-10
+18
-5
+23
+22
+13
-5
+15
+15
-14
-15
+7
-11
-8
-2
-6
-9
-15
-3
+12
+25
-9
-15
-16
+20
+13
+25
-6
+10
+7
+15
-16
+15
-9
-21
+13
+14
+6
-16
+17
-27
-21
+12
+26
+13
+5
-23
+16
+9
+20
+14
-32
+27
-2
-16
+21
-92
-12
-14
-25
+4
-21
-9
-14
-14
-6
+8
+5
+2
-1
-3
+15
+13
+2
-19
-15
+11
+14
-4
-18
+23
-24
-14
+17
-10
+1
+14
-19
-18
-11
-10
-13
+8
+21
-4
-4
+11
-17
-13
-23
-9
+14
+14
-20
-17
+11
-18
-19
-64
+9
-24
-16
-10
+196
+16
-5
+21
-7
+28
+5
+5
-19
+38
-33
+25
+209
+391
-559
+64522
-2
-19
+7
+17
+5
-6
+18
-2
+5
+4
-11
-17
+14
+12
-19
-9
+14
+20
-16
-6
+12
+15
+11
+15
+24
-37
+12
-15
-4
+3
-21
-17
-19
-16
+21
+12
+9
-13
-20
-30
-7
+10
+14
-3
+20
+11
-1
+9
-22
-19
-3
-8
+3
-18
+8
+3
-7
-2
-7
+6
+15
-19
+13
-26
+7
-18
-13
+21
-9
+10
-130255`.split(/\n/).forEach((num,i) => searchIt(num,i))
console.log(res);