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About Function and Parameter

New to Javascript, still confused about parameter

Here are some codes:

var people = [{ 
 name: 'Casey', 
 rate: 60
},
{
 name: 'Camille',
 rate: 80
},
{
 name: 'Gordon',
 rate: 75
},
{
 name: 'Nigel',
 rate: 120
}
];
function priceRange(person) { 
return (person.rate >= 65) && (person.rate <= 90); 
 };
var results = []; 
results = people.filter(priceRange);

I know this is a very basic question, but I just want to know the parameter "person".How did the computer know the parameter "person" is coming from the object "people"?

Answer*

# Data structures : 

 - `[....]` this is an array
 
 - `{attr1:'val1', attr2: 'val2',. ...}` this is a literal object. 

👉🏼 ↪ `people` is an ARRAY of literal object**s** , and each object has two attributes (keys) : name & rate.

# Functional Programming:

Since `people` is an array, Array class provides a set of methods ,namely `filter()` which accepts as first argument : FUNCTION .

`filter()` will run the function (1ˢᵗ argument of `filter`) for each item , then if it returns `true`, it accepts the element , and vice versa . 

Let's take , an example more simple than what you have : let's take `an Array of digits`





 const arrayOfDigits = [23, 400 , 99, 4, 222];


 function exceed100(element) {
 return element > 100;
 }

 console.log(
 arrayOfDigits.filter(exceed100)
 )



example above filters all digits less or equal to 100.and it keep only digits exceeds 100.

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Thanks, I understand how does the filter() works, I just more confuse about the question of transferring parameter. I know person is the parameter in the priceRange() function, but how did "person" came from and why did person.name equals to people.name?

jessica
– jessica

2017年01月23日 03:37:14 +00:00
Commented Jan 23, 2017 at 3:37
Keep the following callback's rule in your mind : You can choose any name for argument (person, element, ...item, however you should keep the order (person is the 1st arg, index is the 2nd arg.. so on)

Abdennour TOUMI
– Abdennour TOUMI

2017年01月23日 05:27:40 +00:00
Commented Jan 23, 2017 at 5:27

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About Function and Parameter

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