Given an array [1, 2, 3, 4]
, how can I find the sum of its elements? (In this case, the sum would be 10
.)
I thought $.each
might be useful, but I'm not sure how to implement it.
Array.prototype.reduce can be used to iterate through the array, adding the current element value to the sum of the previous element values.
console.log(
[1, 2, 3, 4].reduce((a, b) => a + b, 0)
)
console.log(
[].reduce((a, b) => a + b, 0)
)
You get a TypeError
console.log(
[].reduce((a, b) => a + b)
)
console.log(
[1,2,3].reduce(function(acc, val) { return acc + val; }, 0)
)
console.log(
[].reduce(function(acc, val) { return acc + val; }, 0)
)
If non-numbers are possible inputs, you may want to handle that?
console.log(
["hi", 1, 2, "frog"].reduce((a, b) => a + b)
)
let numOr0 = n => isNaN(n) ? 0 : n
console.log(
["hi", 1, 2, "frog"].reduce((a, b) =>
numOr0(a) + numOr0(b))
)
We can use eval to execute a string representation of JavaScript code. Using the Array.prototype.join function to convert the array to a string, we change [1,2,3] into "1+2+3", which evaluates to 6.
console.log(
eval([1,2,3].join('+'))
)
//This way is dangerous if the array is built
// from user input as it may be exploited eg:
eval([1,"2;alert('Malicious code!')"].join('+'))
Of course displaying an alert isn't the worst thing that could happen. The only reason I have included this is as an answer Ortund's question as I do not think it was clarified.