Javascript concatenating numbers, not adding up

问题

It keeps concatenating my numbers into 2111 instead of 5. Why is this? I've tried using parseInt with no luck. res3 btw represents a query into my database that I'm executing.

var dt_total_hours = 0;

            dt_total_hours += res3.fieldByName(dt_cost_per_hour);
            dt_total_hours += res3.fieldByName(dt_prod_dt_hours);
            dt_total_hours += res3.fieldByName(dt_prod_rate);
            dt_total_hours += res3.fieldByName(dt_cost_per_unit);
            dt_total_hours += res3.fieldByName(dt_scrap_startup_cost);
            dt_total_hours += res3.fieldByName(dt_labor_expense);
            dt_total_hours += res3.fieldByName(dt_since_issues_first_noticed);
            dt_total_hours += res3.fieldByName(dt_wo_for_maint);
            dt_total_hours += res3.fieldByName(dt_investigation);
            dt_total_hours += res3.fieldByName(dt_maint_made_bandaid);
            dt_total_hours += res3.fieldByName(dt_parts_outsourcing);
            dt_total_hours += res3.fieldByName(dt_get_equip_out_prod);
            dt_total_hours += res3.fieldByName(dt_perm_repair);
            dt_total_hours += res3.fieldByName(dt_equip_back_to_prod);
            dt_total_hours += res3.fieldByName(dt_to_full_prod_speed);
            dt_total_hours += res3.fieldByName(dt_other);

回答1:

If the values are strings then they will be concatenated, not added numerically.

Try constructing a number from the string value:

dt_total_hours += Number(res3.fieldByName(dt_cost_per_hour));
//                ^------ Force a number here instead of a string.

回答2:

Yeah, it's reading them as strings. I find that a dirty, awful hack to get them interpreted as numbers is to take x += y and change it to x += y / 1.0 (or / 1 for integer). Usually does the trick.

回答3:

you can parse your data according to desired type as follow

dt_total_hours += parseInt(res3.fieldByName(dt_cost_per_hour));

you can also use parseFloat method as well

来源：https://stackoverflow.com/questions/14656003/javascript-concatenating-numbers-not-adding-up