Example 1: array sum javascript const arr = [ 1 , 2 , 3 , 4 ] ; const sum = arr . reduce ( ( a , b ) => a + b , 0 ) ; // sum = 10 Example 2: js sum of array [ 1 , 2 , 3 , 4 ] . reduce ( ( a , b ) => a + b , 0 ) // Output: 10 Example 3: javascript sum of array const sum = arr => arr . reduce ( ( a , b ) => a + b , 0 ) ; Example 4: add all elements in array javascript console . log ( [ 1 , 2 , 3 , 4 ] . reduce ( ( a , b ) => a + b , 0 ) ) console . log ( [ ] . reduce ( ( a , b ) => a + b , 0 ) ) Example 5: sum of all numbers in an array javascript const arrSum = arr => arr . reduce ( ( a , b ) => a + b , 0 ) Example 6: javascript sum array values function getArraySum ( a ) { var total = 0 ; for ( var i in a ) { total += a [ i ] ; } return total ; } var payChecks = [ 123 , 155 , 134 , 205 , 105 ] ; var weeklyPay = getArraySum ( payChecks ) ; ...