How does the alert function work in JavaScript?
Use alert() function to display a popup message to the user. This popup will have OK button to close the popup. The alert function can display message of any data type e.g. string, number, boolean etc.
What does the placeholder attribute do in HTML?
Definition and Usage. The placeholder property sets or returns the value of the placeholder attribute of a text field. The placeholder attribute specifies a short hint that describes the expected value of a text field (e.g. a sample value or a short description of the expected format).
How to display popup message box in JavaScript?
Display Popup Message Box 1 Alert Box. Use alert () function to display a popup message to the user. This popup will have OK button to close the popup. 2 Confirm Box. Sometimes you need to take the user’s confirmation to proceed. 3 Prompt Box. Sometimes you may need to take the user’s input to do further actions in a web page.
Which is paramter does alert ( ) take?
The alert () function takes a paramter of any type e.g., string, number, boolean etc. So, no need to convert a non-string type to a string type. Sometimes you need to take the user’s confirmation to proceed. For example, you want to take the user’s confirmation before saving updated data or deleting existing data.
How to display a popup message in JavaScript?
JavaScript provides different built-in functions to display popup messages for different purposes e.g. to display a simple message or display a message and take user’s confirmation on it or display a popup to take a user’s input value. Use alert() function to display a popup message to the user. This popup will have OK button to close the popup.
How to show loading image when Ajax request is in progress?
If the AJAX request takes more time then at the Client side there is no visible change is been displayed and the user doesn’t know whether its request is in progress or not. You can display a loading image or text message on the page when AJAX request is in progress and hide it after getting a response.
How to check if an image exists in JavaScript?
You can use the basic way image preloaders work to test if an image exists. function checkImage (imageSrc, good, bad) { var img = new Image (); img.onload = good; img.onerror = bad; img.src = imageSrc; } checkImage (“foo.gif”, function () { alert (“good”); }, function () { alert (“bad”); });