如何替换第一个数字？

Question

I believe that it is simple, but currently it isn't working for me... Look what I need below:

seed = 9999;
seed[0] = 1;
seed; //now it's returning 9999, but I want 1999

There are another way to do?

Answer 1

seed is a Number, not a string. You either have to use it as string:

seed='9999';
seed[0]='1';
console.log(seed)//'1999'

Or you can apply a quick fix:

seed=9999;
seed-=8000;
console.log(seed)//1999

Update

You could also make a class to manage the number i that way:

function numArr() {
    this.arr = [];
    this.setNum = function (num) {
        this.arr = [];
        while (num > 10) {//while has digits left
            this.arr.unshift(num % 10);//add digit to array
            num = Math.floor(num / 10);//remove last digit from num
        }
        this.arr.unshift(num)//add the remaining digit
    };
    this.getNum = function () {
        var num = 0;
        for (var i = this.arr.length - 1; i >= 0; i--) {//for each digit
            num += this.arr[i] * Math.pow(10, (this.arr.length - 1 - i))//add the digit*units
        }
        return num;
    }
}

var seed= new numArr();
seed.setNum(9960);
seed.arr[0]=1;
console.log(seed.getNum())//1960
seed.setNum(seed.getNum()+1000);
console.log(seed.getNum())//2960

Answer 2

You can use regex like:

"9999".replace(/[\d]/,"1")

Disclaimer : I am offering an alternate view to problem but of course there is various options to resolve it.

Answer 3

try this

seed = 9999;
seed = seed.toString()
 seed= 1+seed.substr(1, seed.length);
alert(seed);

Answer 4

As is mentioned above the seed is a number not an array ,so you can't do it as you doing it. Look at this:

var seed = (9999 + "").split(""), // Convert the number to string and split it
    seed = ~~(seed[0] = "1", seed.join("")); // Now you can change the first digit then join it back to a string a if you want to you can also convert it back to number

console.log(seed); // 1999

Answer 5

seed = 9999;
var len = seed.toString().length;
var seedAllDigits = seed % (Math.pow(10,len-1));
var finalSeed = "1" + seedAllDigit;

Somethink like this will do the work..

Hope it make sense

Answer 6

9999％1000 + 1000 * 1 == 1999;