What’s a variable?
A variable is solely a spot to retailer one thing. In actual fact, you’ll be able to consider a variable like a cabinet. First, we have to create the cabinet to retailer stuff in. Subsequent, we’ll wish to put one thing within the cabinet. Then later, we’ll wish to retrieve the merchandise and use it. We’d additionally wish to change the merchandise with one other merchandise.
Time to see it in use! Let’s say we needed to alert the quantity
25. Usually, we’d do it like so:
However what about doing this utilizing a variable? Right here’s how:
var x = 25; alert(x);
Let’s check out what’s occurring here- to begin with, we’re creating (aka declaring) our variable known as
x by saying
var x. On this similar line, we’re additionally giving the variable an preliminary worth to retailer by saying
Now, after we run this code it should alert
25! It’s because
x is now only a placeholder for the quantity 25. It is rather like should you have been enhancing a doc and needed to exchange all situations of the phrase “banana” – on this case, the browser goes by way of our code and replaces all situations of the variable
PS: Observe alongside! Create a brand new file known as
index.htmland add the next code:
However why does any of this matter? Nicely, the true energy of variables is the truth that you’ll be able to change them. For instance:
var x = 25; x = 85; alert(x);
As you’ll be able to see, setting a variable that had already been declared is so simple as saying
x = 85. You don’t want the
var bit, because it’s already declared.
Now, we are able to alert
85 with out even altering the road the place it says
Varieties of variables
A string is one other method of claiming some textual content. We’ve to encompass it in quotes as a result of in any other case it will be thought-about a variable. Right here is an instance:
var x = "I'm a string!";
It doesn’t matter you probably have single or double quotes:
var x = 'I'm a string!';
Clearly, we are able to additionally set a variable to a quantity – like we did earlier than! It may be an entire quantity:
var x = 16;
Or a decimal:
var x = three.14;
Booleans are merely
var x = true; var y = false;
This may increasingly sound quite simple, however they’ll come in useful when utilizing
if statements – which allow you to execute bits of your code primarily based on whether or not statements equal
Yay! You now know all about variables! Let’s undergo what we’ve realized as we speak.
To begin with, we realized the way to declare, set and alter variables:
var x = 12; /* Declared and set a variable */ x = "Helloooo!"; /* Change a variable (you'll be able to change it to a special kind) */
We additionally realized about a number of the primary sorts of knowledge:
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false values. See you then!