JavaScript Learning notes a JavaScript what can do

What is a JavaScript?

JavaScript is an interpreted scripting language that can be inserted into an HTML page and interpreted by the browser.

What can two JavaScript do?

① adding new content to HTML

document.write ("

document.write ("<p>this is a paragraph</p>");

Note: Use document.write during HTML output instead of using this method after the document is loaded, otherwise it will overwrite the entire document.

② Response to Events

<button type= "button" onclick= "alert (' welcome! ')" > Click here </button>

The alert () function is often used for code testing, displaying content and judging whether it is expected.

③ changing HTML content

You can use document.getElementById to get to an HTML element and modify its contents to change the HTML content

X=document.getelementbyid ("demo")//Find elements

X.innerhtml= "Hello JavaScript"; Change Content

④ changing HTML images

You can use document.getElementById (' myimage ') to get a picture element and re-assign a value to the path to the element

element.src= New Path

⑤ changing the style of HTML elements

Changing the style of HTML elements is a variant of changing HTML attributes.

X=document.getelementbyid ("demo")//Find element

X.style.color= "#ff0000";

Validate input

JavaScript is often used to validate user input.

Instance

If IsNaN (x) {alert ("Not Numeric")};

JavaScript Learning notes a JavaScript what can do