I am working with firebase and react native.
I have returned an array from my firebase database that looks like this.
[Object, Object, Object]
Under each object I have returned a single item, "level:4".
So I have three objects containing 4,5,6. How do I sum these together?
Thanks!
You can use Javascript's reduce function. This is basically the same as @epascarello answer but in ES6 syntax.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/Reduce
const arr = [{level:2},{level:4},{level:5}];
const total = arr.reduce((prev,next) => prev + next.level,0);
console.log(total);
Either a simple loop
var a = [{level:1},{level:2},{level:3},{level:4}],
total = 0;
for (var i=0; i<a.length; i++) {
total += a[i].level;
}
console.log('total', total)or reduce
var a = [{level:1},{level:2},{level:3},{level:4}]
console.log(a.reduce( function(cnt,o){ return cnt + o.level; }, 0))Use Array.prototype.forEach() method to iterate over your array and sum your elements.
Let us suppose your array is var foo = [object, object, object]
Each object has this structure, { level : 4 }
Write code like this:
var sum = 0;
foo.forEach(function(obj){
sum += obj.level;
});
sum will store the sum
This code will calculate the sum of an array. First, declare one variable; this variable's name will be sum. sum contains the total's sum. Second, declare a numbers variable of type Array. This variable will contain digits.
Then we start a loop (for) operation, in which we assign to the sum variable the value of (sum= sum+i);.
Then we show in (document.write) the numbers and sum.
var summa = 0 , i ;
var numbers= [1,2,3,4,5];
for(i = 0; i <= numbers.length; i++){
summa=summa+i;
}
document.write(numbers , ": bu reqemlerin cemi " ,"=" , summa);
Have you tried accessing the object in the array and calling the property?
var array = [object, object, object];
var sum = array[0].level + array[1].level + array[2].level;
