کار با متد getElementById و innerHTML در جاوا اسکریپت (JavaScript)

<a class="someclass" href="http://example.com/path/to/dir">Old Link</a>
<a id="para">New Link</a>
<script>
function setAttr(){
   let url = document.getElementsByClassName('someclass')[0].getAttribute('href');
   let para = document.getElementById('para');
   
   para.setAttribute("href", url + "/rss");
}
setAttr();
</script>

<style>
#editor {
    width: 500px;
    height: 200px;
	direction: rtl;
	border: 1px solid #E5E5E5;
}
.button {
	border: 1px solid #E5E5E5;
}
blink, .blink {
    animation: blink 1s step-end infinite;
    -webkit-animation: blink 1s step-end infinite;
    -moz-animation: blink 1s step-end infinite;
    -o-animation: blink 1s step-end infinite;
}
@-webkit-keyframes blink {
    80% {
        opacity: 0;
    }
}
@-moz-keyframes blink {
    80% {
        opacity: 0;
    }
}
@-o-keyframes blink {
    80% {
        opacity: 0;
    }
}
@keyframes blink {
    80% {
        opacity: 0;
    }
}
</style>
<script>
function alertThis(text){
alert(text);
}
</script>
<div id="editor" contenteditable="true">نمونه متن... <button class="button" onclick="alertThis('سلام به برنامه خوش آمديد!');"><span class="blink">کليک</span></button></div>

https://searchengineland.com/tested-googlebot-crawls-javascript-heres-learned-220157

<script>
function getSetValue(from, to, num){
    var elm_from = document.getElementById(from);
	var elm_to = document.getElementById(to);
	var value = elm_from.value;
	var result = parseInt(value) * parseInt(num);
	
	elm_to.value = result;
}
</script>
<label for="input-from">فیلد:</label>
<input type="text" id="input-from">
<input type="button" value="ضرب" onclick="getSetValue('input-from', 'input-to', 15);"><br>
<label for="input-to">نتیجه:</label>
<input type="text" id="input-to">

<nav id="menu-top">
<ul>
<li>
</li>
</ul/>
</div>
<input type="button" value="Show/Hide" onclick="toggleShowHide('menu-top');">
<script>
function toggleShowHide(id) {
    var elm = document.getElementById(id);
    var ul = elm.getElementsByTagName('ul')[0];

    if(ul.style.display === 'none'){
        ul.style.display = 'block';
    } else{
        ul.style.display = 'none';
    }
} 
</script>

<script>
function makeTable(div, input) {
var table_div = document.getElementById(div);
var table_input = document.getElementById(input);
var table_value = table_input.value;

var table_tag = document.createElement('TABLE');
table_tag.border = '1';

var table_body = document.createElement('TBODY');
table_tag.appendChild(table_body);

for(var r = 1; r <= table_value; r++) {
var tr = document.createElement('TR');
table_body.appendChild(tr);

for(var d = 1; d <= table_value; d++) {
var td = document.createElement('TD');
td.width = '100';
td.appendChild(document.createTextNode("Cell " + r + "," + d));
tr.appendChild(td);
}
}

table_div.appendChild(table_tag);
}
</script>
<div id="div-test"></div>

<label for="input-test">Table Cells:</label>
<input id="input-test" type="text">

<input type="button" value="Make Table!" onclick="makeTable('div-test', 'input-test');">

<style>
.block {
	width: auto;
	height: 50px;
	border: 1px solid #999;
	margin: 2px;
}
</style>
<script>
var loop = 1;
var last;
function testInnerHTML(sort){
	var elm = document.getElementById('result');
	var div = document.createElement('div');
	div.setAttribute('id', 'block-' + loop);
	div.setAttribute('class', 'block');
	div.innerHTML = 'New Result ' + loop + '!';
	
	if(sort == 'up'){
		elm.appendChild(div);
	} else if(sort == 'down'){
		if(last == 'undefined' || last == null ){
			elm.appendChild(div);
			last = document.getElementById('block-' + loop);
		} else {
			elm.insertBefore(div, last);
			last = document.getElementById('block-' + loop);
		}
	}
	
	loop++;
}
</script>
<div id="result"></div>
<input type="button" value="Test" onclick="testInnerHTML('down');">

<label for="input-1-id">مقدار اول:</label>
<input id="input-1-id" type="text">
<label for="input-2-id">مقدار دوم:</label>
<input id="input-2-id" type="text">
<label for="input-3-id">نتیجه:</label>
<input id="input-3-id" type="text">
<input type="button" value="Click" onclick="doManipulation('input-1-id', 'input-2-id', 'input-3-id')">
<script type="text/javascript">
function doManipulation(id_1, id_2, id_3){
	var input_1 = document.getElementById(id_1);
	var input_2 = document.getElementById(id_2);
	var input_3 = document.getElementById(id_3);
	
	var get = input_1.value * input_2.value;
	input_3.value = get;
}
</script>