how to get false if array have string value of index in javascript-CodePudding


function SummPositive( numbers ) {
  var negatives = [];
  var sum = 0;

  for(var i = 0; i < numbers.length; i  ) {
    if(numbers[i] < 0) {
      negatives.push(numbers[i]);
    }else{
      sum  = numbers[i];
    }
  }

  console.log(negatives);

  return sum;
}

var sum_result = SummPositive( [ 1, 2, 3, 4, 5, -2, 23, -1, -13, 10,-52 ] );

console.log(sum_result);

i have some trouble, i dont know how to check if array have index string, return false, thx all for help me to fix it

CodePudding user response：

function SummPositive( numbers ) {
    let negatives = []; // hold all negative number
    let falsy = false; // boolean to hold true if string exists in the list
  let sum = 0; // to increment all the numbers in the list
  for(let num of numbers) { // loop through the list
    if(typeof num == 'string') {
        falsy = true // set boolean to true if string item exists in the list
      break // break out of the loop
    }
    if (num < 0) {
        negatives.push(num); // push all negative numbers to a negatives list
    } else {
        sum  = num // update sum
    }
  }
  return falsy ? false : sum; // return false if falsy is true else return sum
}

var sum_result = SummPositive([ '44', 1, 2, 3, 4, 5, -2, 23, -1, -13, 10,-52, '3' ]);

CodePudding user response：

The direct answer to your question of "How to check if an array element is a string" is to use the typeof operator, specifically comparing the evaluated result to string:

// const element = array[index];
const isAString = typeof element === 'string';

Here's an example showing how to use various array methods to help with the details of your problem.

function sum (numbers) {
  let sum = 0;
  for (const n of numbers) sum  = n;
  return sum;
}

function sortAndStringify (numbers) {
  // Create a copy so the original object is not mutated by sorting
  const copy = [...numbers];
  return copy.sort((a, b) => a - b).join(', ');
}

function example (array) {
  const stringWasFound = array.some(element => typeof element === 'string');
  console.log('string was found:', stringWasFound);

  // Even better (more strict): ensure that all elements are numbers
  const allElementsAreNumbers = array.every(element => typeof element === 'number');
  console.log('all elements are numbers:', allElementsAreNumbers);

  // Return false if a non-number was found
  if (!allElementsAreNumbers) return false;

  // If we get this far, then we know that we are only dealing with numbers
  const negatives = array.filter(n => n < 0);
  console.log('negatives:', sortAndStringify(negatives));

  const positives = array.filter(n => n >= 0);
  console.log('positives:', sortAndStringify(positives));

  console.log('sum:', sum(positives));
}

console.log('Just numbers:');
example([1, 2, 3, 4, 5, -2, 23, -1, -13, 10, -52]);

console.log('With a string:');
// This one won't make it past the "if" statement
example([1, 2, '3', 4, 5, -2, 23, -1, -13, 10, -52]);

console.log('With a boolean:');
// Neither will this one
example([1, 2, false, 4, 5, -2, 23, -1, -13, 10, -52]);