Array Basic Drills

Accessing Array Items

function accessFirstItem(array) {
  return array[0];
}

function accessThirdItem(array) {
  return array[2];
}




/* From here down, you are not expected to 
   understand.... for now :)  
   
   
   Nothing to see here!
   
*/


// tests

function testFunctionWorks(fn, input, expected) {
  
  if (fn(input) === expected) {
    console.log(`SUCCESS: "${fn.name}" works on [${input}]`);
    return true;
  }
  else {
    console.log(
      `FAILURE: ${fn.name}([${input}]) should be ${expected} but was ${fn(input)}`
    );
    return false;
  }
}


function runTests() {
  
  var list = [1, 4, 9, 16, 25]
  var item1 = 1
  var item2 = 9
  
  var testResults = [
    testFunctionWorks(accessFirstItem, list, item1),
    testFunctionWorks(accessThirdItem, list, item2),
  ];
  
  
  
  var numPassing = testResults.filter(function(result){ return result; }).length;
  console.log(numPassing + ' out of ' + testResults.length + ' tests passing.');
}

runTests();

Adding Array Items

function addToList(list, item) {
  list.push(item);
  return list;
}




/* From here down, you are not expected to 
   understand.... for now :)  
   
   
   Nothing to see here!
   
*/


// tests

function testAddToList() {
  
  const input1 = ["red", "blue", "green"]
  const input2 = "pink"
  const expected = ["red", "blue", "green", "pink"]
  const result = addToList(input1, input2);
  
  if (
    result && result.length && expected.length === result.length &&
    expected.every(function(item) {
      return result.indexOf(item) > -1;
    })) {
    console.log('SUCCESS: `addToList` works!');
  } else {
    console.error('FAILURE: `addToList` is not working');
  } 
}

testAddToList();

Array Length and Access Drill

function findLength(array) {
  return array.length;
}

function accessLastItem(array) {
  return array[array.length - 1];
}




/* From here down, you are not expected to 
   understand.... for now :)  
   
   
   Nothing to see here!
   
*/


// tests

function testFunctionWorks(fn, input, expected) {
  
  if (fn(input) === expected) {
    console.log('SUCCESS: `' + fn.name + '` works on `[' + input + ']`');
    return true;
  }
  else {
    console.error(
      'FAILURE: `' + fn.name + '([' + input + '])` should be ' + expected +
      ' but was ' + fn(input)
    );
    return false;
  }
}

function runTests() {
  
  const list = [1, 4, 9, 16, 25];
  const originalList = [1, 4, 9, 16, 25];
  const length = 5;
  const lastItem = 25;
  
  const testResults = [
    testFunctionWorks(findLength, list, length),
    testFunctionWorks(accessLastItem, list, lastItem),
  ];
  
  
  
  const numPassing = testResults.filter(function(result){ return result; }).length;
  console.log(numPassing + ' out of ' + testResults.length + ' tests passing.');
}

runTests();

Creating Arrays

function makeList(item1, item2, item3) {
  return [item1, item2, item3];
}



/* From here down, you are not expected to 
   understand.... for now :)  
   
   
   Nothing to see here!
   
*/


// tests

function testMakeList() {
  
  const items = ["prime rib", "fried goat cheese salad", "fish tacos"];
  const result = makeList(items[0], items[1], items[2]);
  
  if (
    result && result.length && items.length === result.length &&
    items.every(function(item) {
      return result.indexOf(item) > -1;
    })) {
    console.log('SUCCESS: `makeList` works!');
  } else {
    console.error('FAILURE: `makeList` is not working');
  } 
}

testMakeList();