JavaScript~?

Question

Which of the following will get all the images of a html document?

a) var images=document.getElementsByTagName(images);
b) var images=document.getElementsById("img");
c) var images=document.getElementsByTagName("img");
d) var images=document.getElementsById("images")

I chose b) but it's wrong. I don't understand why...Can someone please explain to me?
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Which of the following is a correct way to handle an event when a button is clicked?

a) onclick=alert('you click me');
b) onclick="alert("you click me");"
c) onclick="alert('you click me');"
d) onclick="alert(you click me);"

I chose a) but it's wrong. Can someone please explain to me?
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Answer 1

You should use document.getElementsByTagName("img");

document.getElementById("id_name") is used to get an element through its id.



Getting all images in an html document means you should search all tags, thus you should use getElementsByTagName.



Regarding question number 2, the correct answer is letter c. The onclick keyword should be used as follows: onclick="script_here".

Also, When declaring strings inside a double quote it should be enclosed in apostrophes (').

Answer 2

In the first question, you need to extract the images from an html document, and you know that to use an image in an html document, you use the tag, right? So you need to use the getElementsByTagName method, and specify "img" for the tag you wish to extract.



In the second question, you need to remember that the data contained in all html variables should be surrounded by quotes, such as or . This is the best way to make certain you are passing the correct data. Without quotes, the spaces in variables would cause the browser to get confused. For example, consider the difference between these two tags:











Which one is the correct one? The first one. Notice how all the data for the href and onclick variables are contained neatly in the double quotes. Your browser would get confused and display a screwed-up page if you used the second tag. Try it on a sample webpage and see for yourself: The webpage will be screwed-up right at the "onclick=alert('you" part, because the space following this will cause the browser to think you're done inputting data into the variable.

Answer 3

1.

I think the answer is c because it is get Elements By Tag Name and I think that the tag name specified is IMG. I cannot tell because your text is not complete.



2.

c onClick requires the action to be in quotes. Javascript requires that you cannot use the same quote characters for different usages. so onClick='alert("you click me");' does the same thing but the otherway around. Of course HTML wants a double quote first. If you need a third level of quote marks then you have to excape the quote mark like \" or \'.



I hope this helps.