Javascript variable in element name

Question

I have a text box, and a select box with choices that are the same as the columns in a table. I want to be able to type in the box, select a column, press a button, and have it copy whatever is in the box, to every box in the column. I am having a hard time with the syntax as using a variable is the only thing that prevents this from working. When I put in real values, it works fine.

function testScript(fill) {
choice=document.form1.column.value;
alert (fill);
alert (choice);
    for($i=0;$i<fill;$i++){
        document.form1.choice[$i].value=document.form1.copy.value;
    }
}

Fill (tested by the alert) provides me with the number of rows in the table and works fine. Choice is my select (drop down) box. If I type in "document.form1.make[$1].value= it fills what I type in every row of the make column. If I choose make in the select box, choice does say make as indicated by my test alert.

Any ideas how to use the variable correctly in the for loop?

nnnnnn · Accepted Answer · 2012-03-10 10:05:07Z

4

If I understand you correctly, the syntax you are looking for is:

document.form1[choice][$i].value=document.form1.copy.value;

In a general sense, to access a property "prop1" of an object obj you can use two syntaxes:

obj.prop1
// or
obj["prop1"]

With the square bracket syntax you can use any expression as long as it evaluates to a string that is the name of the property you want, so:

var x = "prop1";
obj[x]
// or
var x = "pr", y = "op1";
obj[x + y]

...are both going to access the same property as obj.prop1.

Note also that you should declare your choice and $i variables with the var keyword (as in my examples) or they will become global variables.

answered Mar 10, 2012 at 10:05

nnnnnn

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1 Comment

Brian Over a year ago

I believe you understood me correctly, however I had already tried your suggestion and unfortunately it doesn't work. I'm not sure what else to try.

redDevil · Accepted Answer · 2012-03-11 10:37:03Z

0

function testScript(fill) {
    choice=document.form1.column.value+'[]';
    for($i=0;$i<fill;$i++){
        document.form1.elements[choice][$i].value=document.form1.copy.value;
    }
}

Updated

view sample here: jsfiddle link

edited Mar 11, 2012 at 10:37

answered Mar 10, 2012 at 10:08

redDevil

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2 Comments

Brian Over a year ago

I tried your suggestion, but it doesn't work. I've tried many other variations as well. Do you think I need a different approach to the problem or are you sure this is possible. It seems like the best way, but I'm sure.

redDevil Over a year ago

sorry, i have updated the code. I think this is what you needed

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