ArrayMethodsAndTests/every.html at master · joshmerritt/ArrayMethodsAndTests · GitHub

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<script src="../simpletest.js"></script>
<script>

// Prototype Function
//  function every(originalArray, callback) {
//      for(var i = 0; i < originalArray.length; i++) {
//          if(!callback(originalArray[i], i, originalArray)) {
//              return false;
//          }
//      }
//      return true;
//  }


function every(originalArray, callback, optionalThisArgument) {
    var functionCallback = callback;
    var maxRunCount = originalArray.length;
    if(Object.keys(originalArray).length === 0) {
      return true;
    }
    if (arguments.length >= 3) {
      functionCallback = callback.bind(optionalThisArgument);
    }
    for(var i = 0; i < maxRunCount; i++){
        if(i in originalArray && !functionCallback(originalArray[i], i, originalArray)) {
            return false;
        }
    }
    return true;
}

tests({

  'It should immediately return false if the callback returns false for an element': function () {
    var runCount = 0;
    var functionResult = every([1,2,3], function(element){
      runCount++;
      return element < 2;
    })
    eq(functionResult,false);
    eq(runCount,2);
  },

  'It should return true or false.' : function (){
    var functionResult = every([1,2,3], function(element){
      return element < 4;
    })
    eq(functionResult,true);
  },

  'It should pass in the ith element as the first argument to the callback': function() {
    every([3],function(number){
      eq(3, number);
    })
  },

  'It should pass in the ith position as the second arguement to the callback': function() {
    every([1],function(number, index){
      eq(0,index);
    })
  },

  'It should pass in the original array as the third argument to the callback': function() {
    var testArray = [1,2,3];
    every(testArray, function (number, index, originalArray){
      eq(originalArray,testArray);
    })
  },

  'It should accept an optional this object': function () {
    every([1], function() {
      eq(this.description,"I should be accessible within the callback");
    }, {description:"I should be accessible within the callback"})
  },

  'It should not modify the original array': function () {
    var testArray = [1,2,3];
    var testCopy = [1,2,3];
    every(testArray,function (){});
    for(var i = 0; i < testArray.length; i++) {
        eq(testArray[i],testCopy[i]);
    }
    },

  'It should return true for an empty array': function() {
    var functionResult = every([],function(){
      return false;
    });
    eq(functionResult,true);
  },

  'It should run <= originalArray.length times.': function () {
    var runCount = 0;
    every([1,2,3],function(number, index, array){
      runCount++;
      array.push('66');
      return number > 0;
    })
    eq(runCount,3);
  },

  'It should only run for elements in the array.': function() {
    var runCount = 0;
    every([,2,3,4,],function(number, index, array){
      runCount++;
      return number > 0;
    })
    eq(runCount,3);
  }
});
</script>