Compare values from array

Question

I'm taking random values from array A and B and trying to compare their solved values, is not working because values in arrays are strings, how to get them to number and solve them?

.controller('questions', function($scope) {
  var A = ['6-2', '7+3', '8*1', '9/3', '8+1'];
  var B = ['1+5', '7-3', '10-5', '10/2', '3*2'];

  var questionA = A[Math.floor(Math.random() * A.length)];
  var questionB = B[Math.floor(Math.random() * B.length)];

  if (questionA > questionB) {

    console.log('It\'s bigger ');
  } else {

    console.log('It\'s smaller');
  }
});

What do you mean? You want '7+3' to magically be 10?

putvande
– putvande

2016-06-08 07:42:50 +00:00
Commented Jun 8, 2016 at 7:42 — putvande
– putvande, Commented Jun 8, 2016 at 7:42

Martijn Welker · Accepted Answer · 2016-06-08 07:42:55Z

3

You can use $scope.$eval() to get the result of the equation:

var answerA = $scope.$eval(questionA),
    answerB = $scope.$eval(questionB);

if(answerA > answerB)

answered Jun 8, 2016 at 7:42

Martijn Welker

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4 Comments

Martijn Welker Over a year ago

@Rajesh Did you read my answer ? It's using $scope.$eval not js eval

Rajesh Dixit Over a year ago

@MartijnWelker my apologies.

Rajesh Dixit Over a year ago

Found a good answer eval vs $eval. Also @MartijnWelker You can also include $parse. Have not used it but can be good variety for answer.

Martijn Welker Over a year ago

@Rajesh $eval calls $parse internally

Rajesh Dixit · Accepted Answer · 2016-06-08 08:23:33Z

An alternate to eval

JSFiddle

var A = ['6-2', '7+3', '8*1', '9/3', '8+1'];
var B = ['1+5', '7-3', '10-5', '10/2', '3*2'];

var len = Math.max(A.length, B.length);

for (var i = 0; i < len; i++) {
  var r1 = evaluate(A[i]);
  var r2 = evaluate(B[i]);

  var msg = "It's " + (+r1 > +r2 ? "Bigger" : "Smaller");
  console.log(msg, r1, r2);
}

function evaluate(str) {
  var opReg = /[-+\/\*]/g;
  var op_arr = str.match(opReg);
  var result = 0;
  var sortOrder = {
    "*": 1,
    "/": 2,
    "+": 3,
    "-": 4
  }
  op_arr.sort(function(a, b) {
    var s1 = sortOrder[a];
    var s2 = sortOrder[b];
    return s1 > s2 ? 1 : s1 < s2 ? -1 : 0;
  }).forEach(function(op) {
    var val_arr = getValueArr(str, op)
    result = calculate(val_arr, op);
    str = str.replace(val_arr[0] + op + val_arr[1], result)
  });
  return result;
}

function getValueArr(str, op) {
  var r = str.split(op);
  var v1 = 0;
  var v2 = 0;
  var opReg = /[-+\/\*]/g;
  v1 = opReg.test(r[0]) ? r[0].split(opReg).reverse()[0] : r[0];
  v2 = opReg.test(r[1]) ? r[1].split(opReg)[0] : r[1];
  return [v1, v2];
}

function calculate(val, op) {
  switch (op) {
    case "-":
      return +val[0] - +val[1];
    case "+":
      return +val[0] + +val[1];
    case "*":
      return +val[0] * +val[1];
    case "/":
      return +val[0] / +val[1];
  }
  return 0;
}
evaluate('6-2+4*2')

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