Declare
最后更新于：2022-04-01 03:12:37
# Declaring Functions
Functions, like variables, must be declared. Let's declare a function `double` that accepts an **argument** called `x` and **returns** the double of x :
~~~
function double(x) {
return 2 * x;
}
~~~
> *Note:* the function above **may** be referenced before it has been defined.
Functions are also values in JavaScript; they can be stored in variables (just like numbers, strings, etc ...) and given to other functions as arguments :
~~~
var double = function(x) {
return 2 * x;
};
~~~
> *Note:* the function above **may not** be referenced before it is defined, just like any other variable.
Exercise
Declare a function named `triple` that takes an argument and returns its triple.
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