如何在JavaScript中检查字符串是否相等

Question

I'm nearly new to JavaScript.

I want to make a random-name generator where from a string array I get 5 random names. This works, but I want to add many names, and I want to check that no names are duplicated. Because of that, I wanted to make a textfield where I can write names, and with the button press a for-loop looks after the array index, and with an if-statement. T

his is the html code:

<div id="box">
    <p id="first"></p>
    <p id="second"></p>
    <p id="third"></p>
    <p id="fourth"></p>
    <p id="fifth"></p>
</div>
<br>
<input type="button" value="Generier Namen" id="button">

<div>
    <input type="text" placeholder="Name.." id="input">
    <input type="button" value="Checken" id="checkbutton">
    <p id="output"></p>
</div>

and this the JavaScript

let namesMale = ["Akemi", "Akechi", "Akihiko", "Akihiro", "Akira", "Amida", "Arata", "Daisuke", "Eichi", "Eiko", "Hajime", "Haru", "Haruo", "Hikaru", "Hiroshi", "Hiroyuki", "Hisoka", "Hoshi", "Isao", "Izanagi", "Kaori", "Kazuhiko", "Kenji", "Kentaro", "Kichi", "Kioshi", "Kitaro", "Kiyo", "Kiyoshi", "Koshiro", "Masahiro", "Masayuki", "Minori", "Mitsuo", "Namiyo", "Naoko", "Nikko", "Ozuru", "Raidon", "Renjiro", "Ryo", "Ryuji", "Sadao", "Satoshi", "Seiichi", "Shinichi", "Shuji", "Taiyo", "Takahiro", "Takeo", "Takiyo", "Taku", "Tama", "Tatsuo", "Tenchi", "Tetsuya", "Tomo", "Torio", "Toshi", "Toyo", "Tsutomu", "Yasashiku", "Yoshi", "Yoshikazu", "Yoshimitsu", "Yoshinori", "Yoshito", "Yoshiyuki", "Yuji", "Yuki", "Yukio", "Yutaka", "Yuudai", "Zinan"];

    document.getElementById("button").onclick = function() {
        let randomOne = Math.floor(Math.random() * namesMale.length);
        let randomTwo = Math.floor(Math.random() * namesMale.length);
        if(randomTwo == randomOne){
            let randomTwo = Math.floor(Math.random() * namesMale.length);
        }
        let randomThree = Math.floor(Math.random() * namesMale.length);
        if(randomThree == randomOne ||randomThree == randomTwo){
            let randomThree = Math.floor(Math.random() * namesMale.length);
        }
        let randomFour = Math.floor(Math.random() * namesMale.length);
        if(randomFour == randomOne || randomFour == randomTwo || randomFour == randomThree){
            let randomFour = Math.floor(Math.random() * namesMale.length);
        }
        let randomFive = Math.floor(Math.random() * namesMale.length);
        if(randomFive == randomOne || randomFive == randomTwo || randomFive == randomThree || randomFive == randomFour){
            let randomFive = Math.floor(Math.random() * namesMale.length);
        }

        document.getElementById("first").innerHTML = namesMale[randomOne];
        document.getElementById("second").innerHTML = namesMale[randomTwo];
        document.getElementById("third").innerHTML = namesMale[randomThree];
        document.getElementById("fourth").innerHTML = namesMale[randomFour];
        document.getElementById("fifth").innerHTML = namesMale[randomFive];
    }



    document.getElementById("checkbutton").onclick = function() {
        let input = document.getElementById("input").value;
        for(let i = 0; i <= namesMale.length; i++){
            console.log(namesMale[i]);
            if(input.equals(namesMale[i])){
                document.getElementById("output").innerHTML = "Existiert";
            }
            else{
                document.getElementById("output").innerHTML = "Existiert nicht";
            }
        }
    }


//  ####### Event Handler ####### 

    let pressTab = document.getElementById("button");
    pressTab.addEventListener("keyup", function(event){
        if(event.keyCode === 13){
            event.preventDefault();
            document.getElementById("set").click();
        }
    });

The way I want it to work works in C# and Java, but my problem is, that the chrome console says: Uncaught TypeError: input.equals is not a function

How can I make it works, because in the documentation I found nothing..

Edit: I forgot to say that "===" and "==" will get me (if the name is in the list or not) "Existiert nicht" in english "don't exist"

Answer 1

You can use == to check the equality

 let namesMale = ["Akemi", "Akechi", "Akihiko", "Akihiro", "Akira", "Amida", "Arata", "Daisuke", "Eichi", "Eiko", "Hajime", "Haru", "Haruo", "Hikaru", "Hiroshi", "Hiroyuki", "Hisoka", "Hoshi", "Isao", "Izanagi", "Kaori", "Kazuhiko", "Kenji", "Kentaro", "Kichi", "Kioshi", "Kitaro", "Kiyo", "Kiyoshi", "Koshiro", "Masahiro", "Masayuki", "Minori", "Mitsuo", "Namiyo", "Naoko", "Nikko", "Ozuru", "Raidon", "Renjiro", "Ryo", "Ryuji", "Sadao", "Satoshi", "Seiichi", "Shinichi", "Shuji", "Taiyo", "Takahiro", "Takeo", "Takiyo", "Taku", "Tama", "Tatsuo", "Tenchi", "Tetsuya", "Tomo", "Torio", "Toshi", "Toyo", "Tsutomu", "Yasashiku", "Yoshi", "Yoshikazu", "Yoshimitsu", "Yoshinori", "Yoshito", "Yoshiyuki", "Yuji", "Yuki", "Yukio", "Yutaka", "Yuudai", "Zinan"]; function findName(val) { for (let i = 0; i <= namesMale.length; i++) { console.log(namesMale[i]); if (val == namesMale[i]) { console.log("Existiert"); } else { console.log("Existiert nicht"); } } } findName('Yuki'); 

You can also use a function indexOf to find if particular string is present in an array

 let namesMale = ["Akemi", "Akechi", "Akihiko", "Akihiro", "Akira", "Amida", "Arata", "Daisuke", "Eichi", "Eiko", "Hajime", "Haru", "Haruo", "Hikaru", "Hiroshi", "Hiroyuki", "Hisoka", "Hoshi", "Isao", "Izanagi", "Kaori", "Kazuhiko", "Kenji", "Kentaro", "Kichi", "Kioshi", "Kitaro", "Kiyo", "Kiyoshi", "Koshiro", "Masahiro", "Masayuki", "Minori", "Mitsuo", "Namiyo", "Naoko", "Nikko", "Ozuru", "Raidon", "Renjiro", "Ryo", "Ryuji", "Sadao", "Satoshi", "Seiichi", "Shinichi", "Shuji", "Taiyo", "Takahiro", "Takeo", "Takiyo", "Taku", "Tama", "Tatsuo", "Tenchi", "Tetsuya", "Tomo", "Torio", "Toshi", "Toyo", "Tsutomu", "Yasashiku", "Yoshi", "Yoshikazu", "Yoshimitsu", "Yoshinori", "Yoshito", "Yoshiyuki", "Yuji", "Yuki", "Yukio", "Yutaka", "Yuudai", "Zinan"]; function findName(val) { if (namesMale.indexOf(val) != -1) { console.log(val+" Existiert"); } else { console.log(val+" Existiert nicht"); } } findName('Yuki'); findName('ABC'); 

Answer 2

String has no such method equals . Neither you have defined on its prototype. You could check rather like this:

if(input == namesMale[i]){

Or,

if(input === namesMale[i]){ // strictly compare

Answer 3

As per error mentioned in question you are facing error below

if(input.equals(namesMale[i])){  //Error is here, javascript does not contain .equal method
                document.getElementById("output").innerHTML = "Existiert";
            }
            else{
                document.getElementById("output").innerHTML = "Existiert nicht";
            }

You can try with

if(input === namesMale[i]) //=== triple equal to check type and value 

or

 if(input == namesMale[i]) //== double equal for testing loose equality

Answer 4

Unfortunately, there is no equals function for strgins comparison in JavaScript. So, instean of that you can check if these two strings are equal with === operator. Overall, your function must look like:

document.getElementById("checkbutton").onclick = function() {
    let input = document.getElementById("input").value;
    for(let i = 0; i <= namesMale.length; i++){
        console.log(namesMale[i]);
        if(input === namesMale[i]){
            document.getElementById("output").innerHTML = "Existiert";
        }
        else{
            document.getElementById("output").innerHTML = "Existiert nicht";
        }
    }
}

Hope it helped, Cheers!