calculate sum in iteractive grid

Dear;
I appriciate your co-operation in this forum.

I use the following code which is get from this site to calculate sum in iteractive grid
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var model = apex.region("test_ig").widget().interactiveGrid("getViews", "grid").model;

var totAmount = 0;
var vSign = parseFloat(-1);

model.forEach(function(r) {
var actionType = model.getValue(r,"ACTION_TYPE").v;
var v_jdAmount = parseFloat(model.getValue(r,"JD_AMOUNT"));

if (!isNaN(v_jdAmount)) {
if (actionType == 'C') totAmount += v_jdAmount;
if (actionType == 'D') totAmount += -1*v_jdAmount;
console.log("it is "+ actionType + " " + v_jdAmount);
}

});
$s('P33_TOTAL',totAmount);
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i think in this statement
var actionType = model.getValue(r,"ACTION_TYPE").v; -----error

i need refresh summation where i select delete before commit.

thanks in advanced