What exactly are function parameters?

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I don't really understand them at all. The most I know is this:

JavaScript

function Test(a, b) {
alert(a + b);
}

Test("Hello ", "World!");
//Alerts "Hello World!"

I understand what a and b is in this function. But in the next example, I have no idea what a and b are. Take a look:

JavaScript

function Sort() {
var arr = [31, 1, 71, 500];
arr.sort(function(a, b) {return a - b});
alert(arr);
}
//Alerts "1,31,71,500". Without the parameters, it sorts as "1,31,500,71".

But I still don't know what a and b are, or how they managed to sort it correctly.

What I have tried:

Nothing. Nobody on Sololearn understood my question, so now i'm here. xD

Posted 1-Aug-18 13:05pm

Member 13934693

Updated 1-Aug-18 15:50pm

Blutfaust

v2

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Mohibur Rashid · Answer 1 · 2018-08-01T13:54:00

sort function of javascript array object take 1 parameter or no parameter.

what would happen if no paramerter? it sort alphabetically. in order to tell javascript howyou want to sort you need to pass a function as parameter to sort function. The parameter function takes two arguments and either zero or positive non zero or negative non zero (haha)

funtion comp(a, b) {
 return a-b; // 0 means equal, negative means a is small.
}
arr.sort(comp);

in your example your function is anonymous. this fuction is not reusable and will be lost after execution

I will give you an example, so that you can understand anonymous function.

Let's say we have a function that produce "hello world". But the function itself do not render the result. Instead function uses provided mechanism to represent data.

function HelloWorld(func) {
 // we will use this func to render the result
 var result="Hello World";
 func(result); // we are using func as a function 
}

// now let's use HelloWorld function to utilize data; 
function DisplayToDiv(res) {
 document.getElementById("divid").innerHtml = res;
} 

// call the function
HelloWorld(DisplayToDiv); 

// let's write the next command to output as console result 

HelloWorld(function /*name is not required*/(res){
 console.log(res);
});

// another example
HelloWorld(alert); // does alert look familiar to you?

Hope this helps

Oh!! by the way, this function that you pass is called call back function