index.js

Array length and access drill

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

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

/* In the 2nd function, why is the array before the [array.length - 1] necessary?

/* 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();

https://repl.it/@liseferguson/Adding-array-items-drills