[Java Script] Finding HTML Elements

Finding HTML Element by Id

var myElement = document.getElementById("intro");

Finding HTML Elements by Tag Name

var x = document.getElementsByTagName("p"); 

Finding HTML Elements by Class Name

var x = document.getElementsByClassName("intro");

Finding HTML Elements by CSS Selectors

var x = document.querySelectorAll("p.intro");

Finding HTML Elements by HTML Object Collections

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
    var x = document.forms["frm1"];
    var text = "";
    var i;
    for (i = 0; i < x.length ;i++) {
        text += x.elements[i].value + "<br>";
    }
    document.getElementById("demo").innerHTML = text;
}
</script>

命名規則:

變數與函式，都用小駝峰式(camelCase)的命名。類別用巴斯卡(PascalCase)或大駝峰式命名法(CamelCase)命名: