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.

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