JavaScript function between two numbers in a list? - arrays

Question

I would like to create a function which will retrieve the result from following list
var Fedsy = [
{min : 0, max : 2300 , must:0, percent:0 , excess:0},
{min : 2300, max : 11525 , must:0, percent:10 , excess:2300},
{min : 11525, max : 39750 , must:922.50, percent:15 , excess:11525},
{min : 39750, max : 93050 , must:5156.25, percent:25 , excess:39750},
{min : 93050, max : 191600 , must:18481.25, percent:28 , excess:93050},
{min : 191600, max : 413800 , must:46075.25, percent:33 , excess:191600},
{min : 413800, max : 415500 , must:119401.25, percent:35 , excess:413800},
{min : 415500, max : 1000000000 , must:119996.25, percent:39.6 , excess:415500}
];
Now I want to pull the row from above list if "inputNum" is between "min" & "max"
var result= function(inputNum){
///..???
}
Ex:if "inputNum"= 40000 the function should return
{min : 39750, max : 93050 , must:5156.25, percent:25 , excess:39750}

Answer 1

Since you tagged underscore.js, I understand that you want to solve the problem using that library.
As such, you can use the function _.find to find the first value that matches a condition. Think of it like a filter but just looking into the first one:
function findRange(inputNum) {
return _.find(Fedsy, function(f) {
return f.min <= inputNum && f.max >= inputNum;
});
}
The first item from Fedsy (f) to return true in the iterator function will be the value that underscore returns.
You may see it more in detail and with more reference functions at underscore.js site: http://underscorejs.org/

Answer 2

What I did:
I created the function you mentioned, it uses pure javascript without any libraries. It loops through each item in the Fedsy array, and looks to see if the value is in the range. If so it returns the row in question.
It also returns as soon as it finds the result not continuing to search the object.
Data
var Fedsy = [
{min : 0, max : 2300 , must:0, percent:0 , excess:0},
{min : 2300, max : 11525 , must:0, percent:10 , excess:2300},
{min : 11525, max : 39750 , must:922.50, percent:15 , excess:11525},
{min : 39750, max : 93050 , must:5156.25, percent:25 , excess:39750},
{min : 93050, max : 191600 , must:18481.25, percent:28 , excess:93050},
{min : 191600, max : 413800 , must:46075.25, percent:33 , excess:191600},
{min : 413800, max : 415500 , must:119401.25, percent:35 , excess:413800},
{min : 415500, max : 1000000000 , must:119996.25, percent:39.6 , excess:415500}
];
Function
function filterArray(inputNum){
var row;
// Foreach item in the array
for(rownum in Fedsy){
var row = Fedsy[rownum];
// If "inputNum" is greater than or equal to "row.min" & less than "row.max"
if(inputNum >= row.min && inputNum < row.max){
return row;
}
}
}
Usage
var result = filterArray(3); // returns first row
console.log(result.must); //0

Answer 3

If you just want the first matching row, then and application of underscore/lodash's _.find https://lodash.com/docs#find might be what you want:
var result = (function(inputNum){
return _.find(Fedsy, function(item){
return inputNum>item.min && inputNum<item.max;
});
})();
That will immediately run an anonymous function that accepts the inputNum and uses it in another anonymous function that _.find uses to check each item. The advantage of _.find is that it will stop looking as soon as it hits a result.
Ideally though, you'd write things in a more generalized way, so that you could specify your filter and what you're filtering separately, so maybe by doing something like this:
var minmaxFilterFunc = function(inputNum){
return function(item){
return inputNum>item.min && inputNum<item.max;
};
};
Now, using minmaxFilterFunc, you can create a function that will return true for a particular inputNum. Now you can use find directly, creating the proper filter function in one line. Easier to read, and also easier to reuse for filtering other collections on different numbers later.
var result = _.find(Fedsy, minMaxFilterFunc(inputNum));