need help creating a if statement with a loop

Question

I need some help with writing a loop. I'm still learning javascript and here is what i've done when manually creating the variables. As you can see I am basically creating three variables but because I dont know how to put this in a loop I have to manually declare each variable which is a pain as the input increases. For example this is really 4 items and there calories. If I wanted to do 20 items and there calories it would be a nightmare. what I would like to do is ask a if statement that ask's how many items did i eat today and the loop would then ask for the information below and stop when the if statement was satisfied.

var Food1 = window.prompt("What did you eat today?");
var Cal1 = window.prompt("How many calories was " + Food1);
var num1 = parseInt(Cal1);
var Food2 = window.prompt("What did you eat today?");
var Cal2 = window.prompt("How many calories was" + " " + Food2);
var num2 = parseInt(Cal2);
var Food3 = window.prompt("What did you eat today?");
var Cal3 = window.prompt("How many calories was " + Food3);
var num3 = parseInt(Cal3);
var Food4 = window.prompt("What did you eat today?");
var Cal4 = window.prompt("How many calories was" + " " + Food4);
var num4 = parseInt(Cal4);

your ask in prompt may be different ?

daremachine
– daremachine

2015-03-03 01:42:49 +00:00
Commented Mar 3, 2015 at 1:42 — daremachine
– daremachine, Commented Mar 3, 2015 at 1:42

royhowie · Accepted Answer · 2015-03-03 01:50:15Z

2

// prompt for number of foods
var n = parseInt(window.prompt("How many food items?"));
var food = [];
// we will loop through and ask n times
for (var i = 0; i < n; i++) {
    // ask the user for the name of the food
    var name = window.prompt("Enter name of food:");
    // and ask how many calories said food item is
    var calories = parseInt(window.prompt("How many calories was " + name + "?"));
    // create an object to store the food's name and calories
    var foodItem = {
        name: name,
        calories: calories
    }
    // push this to our array
    food.push(foodItem);
}
// now, we can access our food items like this:
// food[0] will return the first food item in our array
// food[0].name will return the first item's name, e.g., "Chipotle Burrito"
// food[0].calories will return its calories, e.g., 9000

answered Mar 3, 2015 at 1:50

royhowie

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5 Comments

royhowie Over a year ago

@DavidCurtis Yeah! You would want to do something like var calTotal=0; for (int i = 0; i < food.length; i++) { calTotal += food[i].calories;} No need to parseInt the calories again, if you've already stored them as a number.

royhowie Over a year ago

@DavidCurtis You could also do: var calTotal = food.reduce(function (p, c) {return p + c.calories }, 0);

David Curtis Over a year ago

the first option makes sense, however its returning the last value i entered instead of the Sum of food[i].calories when i use an alert(calTotal)

royhowie Over a year ago

@DavidCurtis are you using calTotal += food[i].calories? Make sure you haven't made a typo. Sounds like you're just using an equals sign.

David Curtis Over a year ago

perfect, i had a typo and i had var calTotal=0; for (i = 0; i < food.length; i++) { calTotal = food[i].calories; } instead of var calTotal=0; for (i = 0; i < food.length; i++) { calTotal += food[i].calories; } that makes sense

aa333 · Accepted Answer · 2015-03-03 02:06:42Z

2

var foods = []
var calories = []
var num_of_foods = window.prompt("How many foods did you eat today?");
for(var i=0; i<num_of_foods; i++){
   var Food = window.prompt("What did you eat today?");
   var Cal = window.prompt("How many calories was " + Food);
   //Do whatever with Food and Cal
   foods.push(Food)
   calories.push(Cal)
}

Later when you need the collected values you can do:

for(var i=0; i<foods.length; i++){
   food = foods[i]
   calorie = calories[i]
   //Use food and and calorie here 
}

edited Mar 3, 2015 at 2:06

answered Mar 3, 2015 at 1:41

aa333

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1 Comment

jfriend00 Over a year ago

This doesn't actually store the result anywhere useful so doesn't solve that part of the problem. It also doesn't show how to get multiple prompts from a data structure which is also required. This is about 1/3 of a solution to what the OP asked for.

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