CODEWITHSUNDEEP
javascriptif-statementargumentsconditional-statements
akinuri
akinuri

Reputation: 12027

Create an if condition dynamically

I have the following array and I created a function to return items from the array based on the passed filter.

var students = [
    //name      grade   room        gender
    ["name1",   80,     "Farabi",   "K"],
    ["name2",   73,     "B1",       "K"],
    ["name3",   73,     "B1",       "K"],
    ["name4",   60,     "Farabi",   "K"],
    ["name5",   80,     "B1",       "E"],
    ["name6",   43,     "Farabi",   "E"],
];

function getGrades() {
    var grades = [];
    for (var i = 0; i < students.length; i++) {
        if (students[i][arguments[0][1]] == arguments[0][0]) {
            grades.push(students[i][1]);
        }
    }
    return grades;
}

getGrades(["E", 3]); // [gender, column index]

This works as long as I pass a single filter. If I want to pass two filters, e.g., getGrades(["E", 3], ["B1", 2]) it won't work.

I need a way to configure (extend) the if condition students[i][arguments[0][1]] == arguments[0][0] based on the passed arguments.

For getGrades(["E", 3], ["B1", 2]), if condition should be

students[i][arguments[0][1]] == arguments[0][0] && students[i][arguments[1][1]] == arguments[1][0]

How can I dynamically create an if condition?

Upvotes: 0

Views: 4889

Answers (2)

Bhabishya Kumar
Bhabishya Kumar

Reputation: 731

An alternate getGrades implementation using Functional Programming 

var students = [
    //name      grade   room        gender
    ["name1",   80,     "Farabi",   "K"],
    ["name2",   73,     "B1",       "K"],
    ["name3",   73,     "B1",       "K"],
    ["name4",   60,     "Farabi",   "K"],
    ["name5",   80,     "B1",       "E"],
    ["name6",   43,     "Farabi",   "E"],
];


function getGrades(){
  var filters = Array.prototype.slice.call(arguments); //converts all passed filters to array
  return filters.reduce(function(result,filter){       //result is filtered student list till now
      return result.filter(function(student){          //return new filtered list
        return student[filter[1]] === filter[0];
      });
  },students).map(function(student){                   //map filtered students to their grades
      return student[1];
  })
}

document.write(getGrades(["E", 3], ["B1", 2]));

Upvotes: 0

Mike Cluck
Mike Cluck

Reputation: 32511

Rather than trying to dynamically create an if condition, you can iterate through each of the arguments and check them individually. If one of them fails, they all fail. Likewise, if none of them fails, you know that the total result is valid.

for (var i = 0; i < students.length; i++) {
  var student = students[i];
  var matched = true; // This won't change if all of the conditions pass
  for (var j = 0; j < arguments.length; j++) {
    var filter = arguments[j];
    if (student[filter[1]] !== filter[0]) {
      matched = false; // One of the conditions failed, don't check the rest
      break;
    }
  }
  if (matched) {
    grades.push(student[1]);
  }
}

Upvotes: 1

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