Loops

Saturday, June 13, 2020

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1. Iterate with JavaScript While Loops

The first type of loop we will learn is called a while loop because it runs “while” a specified condition is true and stops once that condition is no longer true.

// Setup
var myArray = [];

var i = 5;
while (i >=0){
  myArray.push(i);
  i--;
}

2. Iterate with JavaScript For Loops

// Setup
var myArray = [];

for (var i = 1; i < 6; i++){
  myArray.push(i);
}

3. Iterate Through an Array with a For Loop

// Setup
var myArr = [ 2, 3, 4, 5, 6];

// Only change code below this line
var total = 0;
for (var i= 0; i< myArr.length; i++){
  total += myArr[i]; 
}

4. Nesting For Loops

  for (var i = 0; i < arr.length; i++) {
    for (var j = 0; j < arr[i].length; j++) {
      product *= arr[i][j];
    }
  }

5. Iterate with JavaScript Do…While Loops

Essentially, a do…while loop ensures that the code inside the loop will run at least once

// Change the while loop in the code to a do...while loop so the loop will push only the number 10 to myArray, and i will be equal to 11 when your code has finished running. 
var myArray = [];
var i = 10;

do {
  myArray.push(i);
  i++;
} while (i<5);

6. Replace Loops using Recursion

The recursive version of multiply breaks down like this. In the base case, where n <= 0, it returns 1. For larger values of n, it calls itself, but with n - 1. That function call is evaluated in the same way, calling multiply again until n <= 0. At this point, all the functions can return and the original multiply returns the answer.

Note: Recursive functions must have a base case when they return without calling the function again (in this example, when n <= 0), otherwise they can never finish executing.

  function multiply(arr, n) {
    if (n <= 0) {
      return 1;
    } else {
      return multiply(arr, n - 1) * arr[n - 1];
    }
  }

// Setup
var contacts = [
    {
        "firstName": "Akira",
        "lastName": "Laine",
        "number": "0543236543",
        "likes": ["Pizza", "Coding", "Brownie Points"]
    },
    {
        "firstName": "Harry",
        "lastName": "Potter",
        "number": "0994372684",
        "likes": ["Hogwarts", "Magic", "Hagrid"]
    },
    {
        "firstName": "Sherlock",
        "lastName": "Holmes",
        "number": "0487345643",
        "likes": ["Intriguing Cases", "Violin"]
    },
    {
        "firstName": "Kristian",
        "lastName": "Vos",
        "number": "unknown",
        "likes": ["JavaScript", "Gaming", "Foxes"]
    }
];


function lookUpProfile(name, prop){
// Only change code below this line
  for (var i =0; i <contacts.length; i++){
      if (contacts[i].firstName == name){
          for (var j = 0; j < contacts[i].length; j++){
              if (j == prop){
                  return contacts[i][prop]
              } else {
                  return "No such property"
                  }  
        }
        } else {
            return "No such contact"  
  }
// Only change code above this line
}c
}

lookUpProfile("Akira", "likes");

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