JavaScript Array.shift无效

Question

我一直在编写一个应该删除数组第一个索引的系统.控制台没有将数组从(即)"1,2,3,4,5"更改为"2,3,4,5",而是出现错误:"未捕获的TypeError:num.splice不是函数".我听说num.splice 不是一个函数,它是一个删除数组的第一个索引值的操作(或其他东西).我很困惑,当我使用w3Schools的示例代码时,控制台中没有输出错误.我不明白为什么会这样.

(我已经给出了整个代码以防它与语法问题有关)

function dCrypt() {
    var num = document.getElementById("demoin").value; // ex: a127
    var key = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"];
    var mod = 0;
    var out = 0;
    var prep = 0;
    var pre = 0;
    num.split("");
    mod = num[0];
    pre = key.indexOf(mod);
    num.splice(0,1);
    for (i=0;i <= pre;i++) {
        prep += 26;
    }
    out = Math.floor(num + pre);
    document.getElementById("demoout").innerHTML = out;
}

提前致谢!

Answer 1

当您拆分'num'时,您必须重新分配它

num = num.split("");