如何检查 NodeJS 中的 JSON 是否为空？

Question

I have a function that checks to see whether or not a request has any queries, and does different actions based off that. Currently, I have if(query) do this else something else. However, it seems that when there is no query data, I end up with a {} JSON object. As such, I need to replace if(query) with if(query.isEmpty()) or something of that sort. Can anybody explain how I could go about doing this in NodeJS? Does the V8 JSON object have any functionality of this sort?

Answer 1

You can use either of these functions:

// This should work in node.js and other ES5 compliant implementations.
function isEmptyObject(obj) {
  return !Object.keys(obj).length;
}

// This should work both there and elsewhere.
function isEmptyObject(obj) {
  for (var key in obj) {
    if (Object.prototype.hasOwnProperty.call(obj, key)) {
      return false;
    }
  }
  return true;
}

Example usage:

if (isEmptyObject(query)) {
  // There are no queries.
} else {
  // There is at least one query,
  // or at least the query object is not empty.
}

Answer 2

You can use this:

var isEmpty = function(obj) {
  return Object.keys(obj).length === 0;
}

or this:

function isEmpty(obj) {
  return !Object.keys(obj).length > 0;
}

You can also use this:

function isEmpty(obj) {
  for(var prop in obj) {
    if(obj.hasOwnProperty(prop))
      return false;
  }

  return true;
}

If using underscore or jQuery , you can use their isEmpty or isEmptyObject calls.

Answer 3

Object.keys(myObj).length === 0;

As there is need to just check if Object is empty it will be better to directly call a native method Object.keys(myObj).length which returns the array of keys by internally iterating with for..in loop.As Object.hasOwnProperty returns a boolean result based on the property present in an object which itself iterates with for..in loop and will have time complexity O(N2).

On the other hand calling a UDF which itself has above two implementations or other will work fine for small object but will block the code which will have severe impact on overall perormance if Object size is large unless nothing else is waiting in the event loop.

Answer 4

If you have compatibility with Object.keys , and node does have compatibility, you should use that for sure.

However, if you do not have compatibility, and for any reason using a loop function is out of the question - like me, I used the following solution:

JSON.stringify(obj) === '{}'

Consider this solution a 'last resort' use only if must.

See in the comments "there are many ways in which this solution is not ideal".

I had a last resort scenario, and it worked perfectly.

Answer 5

My solution:

let isEmpty = (val) => {
    let typeOfVal = typeof val;
    switch(typeOfVal){
        case 'object':
            return (val.length == 0) || !Object.keys(val).length;
            break;
        case 'string':
            let str = val.trim();
            return str == '' || str == undefined;
            break;
        case 'number':
            return val == '';
            break;
        default:
            return val == '' || val == undefined;
    }
};
console.log(isEmpty([1,2,4,5])); // false
console.log(isEmpty({id: 1, name: "Trung",age: 29})); // false
console.log(isEmpty('TrunvNV')); // false
console.log(isEmpty(8)); // false
console.log(isEmpty('')); // true
console.log(isEmpty('   ')); // true
console.log(isEmpty([])); // true
console.log(isEmpty({})); // true

Answer 6

const isEmpty = (value) => (
    value === undefined ||
    value === null ||
    (typeof value === 'object' && Object.keys(value).length === 0) ||
    (typeof value === 'string' && value.trim().length === 0)
  )

module.exports = isEmpty;