从 JavaScript 中的数组中选择随机元素返回整个数组

Question

I'm writing a program to guess input using JavaScript, and to do it I have to pick a random element from an array. However, after trying to debug it with Chrome DevTools, I found out that it's returning the whole array instead of just the element. EDIT: I also made sure it had nothing to do with the method used to select a random element. Here's some code:

        var alphabet = ["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","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","0","1","2","3","4","5","6","7","8","9","~","`","!","@","#","$","%","^","&","*","(",")","-","_","=","+","[","]","{","}","\\","|",";",":","'","\"",",","<",".",">","/","?"," "]
        var charset = [];
        if(document.getElementById("lowercase").checked){
            charset.push(alphabet.slice(0, 26));
        }
        if(document.getElementById("uppercase").checked){
            charset.push(alphabet.slice(26, 52));
        }
        if(document.getElementById("numbers").checked){
            charset.push(alphabet.slice(52, 62));
        }
        if(document.getElementById("special").checked){
            charset.push(alphabet.slice(62, alphabet.length));
        }
        var word = document.getElementById("input").value;
        var foundword = "";
        while(true) {
            for(i = 0; i < word.length; i++) {
                foundword += charset[Math.floor(Math.random() * charset.length)];
            }
            if(word == foundword) {
                alert("done");
                break;
            }
            foundword = "";
        }

Could anyone help? Thanks in advance!

Answer 1

alphabet.slice returns an array.

When you charset.push(alphabet.slice(.......)) you are pushing an array, so at the end charset is an array of arrays.

You can use the spread operator - ... - to have the pushed array converted to a series of values:

charset.push(...alphabet.slice(26, 52));

Just to help you get used to the syntax, here are a couple more examples:

let arr = alphabet.slice(26, 52);
charset.push(...arr);

charset.push(...['a', 'b', 'c']);