javascript - Get nth value in array sum of all values -

javascript - Get nth value in array sum of all values -

i have array of elements, need add together every first, seven, 13 , 19 (70, 74, 50, 70) values , sum of them using java script.

var rowspanheight = ['70', '70', '70', '70', '70', '70','74', '74', '74', '74', '74', '74','50', '50', '50', '50', '50', '50','70', '70', '70', '70', '70', '70'];

anyone can help? thanks!

i assume question have add together them whenever alter in array, in case can use:

function sumifdifferent( inputarr ) { var lastnum = -1; var total = 0; (var = 0, l = inputarr.length; < l; i++) { num = parseint(inputarr[i], 10); if (num != lastnum) { lastnum = num; total+=num; } } homecoming total; } alert(sumifdifferent(['70', '70', '70', '70', '70', '70','74', '74', '74', '74', '74', '74','50', '50', '50', '50', '50', '50','70', '70', '70', '70', '70', '70']));

javascript for-loop