check if every object property in object array is not empty string

You could use .some, .every and Object.values:

const arr = [{capacity: ""}, {color: ""}]
const someAreNotEmpty = arr.some((el) => Object.values(el).every(e => e !== ''));

console.log(someAreNotEmpty)

const arr2 = [{capacity: "2"}, {color: ""}]
const someAreNotEmpty2 = arr2.some((el) => Object.values(el).every(e => e !== ''));

console.log(someAreNotEmpty2)

You can iterate through each object using forEach and, then use for..in to access each property and check if its value is an empty string.

const arr = [{capacity: ""}, {color: ""}, {size: "12"}];
const newArr = []

arr.forEach(i => {
  for (const property in i) {
    if (i[property] === '') newArr.push(false);
    else {
      newArr.push(true);
    } 
  }
});

console.log(newArr);

You can walk through the array and check for the property value:

const arr = [{capacity: ""}, {color: ""}, {yes: "indeed"}];
let allSet = true;
arr.forEach(o => {
  let keys = Object.keys(o);
  if(keys.length && !o[keys]) {
    allSet = false;
  }
});
console.log('arr: ' + JSON.stringify(arr));
console.log('allSet: ' + allSet);

Output:

arr: [{"capacity":""},{"color":""},{"yes":"indeed"}]
allSet: false

Solution using Object.values

const arr1 = [{capacity: ""}, {color: ""}];
const arr2 = [{capacity: "full"}, {color: "blue"}];
const arr3 = [{capacity: ""}, {color: "blue"}];

function arePropertiesEmpty( arr){

    for( let i = 0 ; i < arr.length ; i++){
        // values is not empty
        if( Object.values(arr[i])[0].length ) {
            return false;
        }
    }
    return true;
}

// another solution
function arePropertiesEmpty2( arr){

    let filterArr =  arr.filter(eliminateEmptyElementsFromArray);  

    function eliminateEmptyElementsFromArray( el ){
        return Object.values(el)[0].length > 0
    }

    return filterdArr.length > 0 ? false : true;
}

console.log(arePropertiesEmpty(arr1));//true
console.log(arePropertiesEmpty(arr2));//false
console.log(arePropertiesEmpty(arr3));//false

console.log(arePropertiesEmpty2(arr1));//true
console.log(arePropertiesEmpty2(arr2));//false
console.log(arePropertiesEmpty2(arr3));//false