Where do you put parentheses in the following javascript statement

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Hello,

Where do you put parentheses in this Javascript statement:

JavaScript

var temp = da >= d3_svg_arcMax ? r0 ? "Z" : "M0" : r0 ? "M" : "M";

This structure is used in d3 library and it's very confusing for me.

Thank you

What I have tried:

I looked for the answer on the internet but I couldn't find anything helpful. I also tried to debug and use breakpoints to find which operator has the higher priority but it didn't help me neither.

Posted 10-Aug-16 5:39am

Saman With You

Updated 10-Aug-16 5:51am

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David_Wimbley 10-Aug-16 11:43am

What makes you think it needs a parenthesis? What do you want in parenthesis?

The following code compiles and runs so i don't know what the issue is.

var da = "2";
var d3_svg_arcMax = "3";
var r0 = "3";

var temp = da >= d3_svg_arcMax ? r0 ? "Z" : "M0" : r0 ? "M" : "M";
console.log("temp: " + temp);

Saman With You 10-Aug-16 11:48am

I can't trace it. I need to know what is the priority of the operations. Which variable goes into "temp" at the end and why?

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F-ES Sitecore · Accepted Answer · 2016-08-10T05:51:00

It is a little confusing. Here is the outer operation

var temp = da >= d3_svg_arcMax ? X : Y;

This means if da>=d3_svg_arcMax then temp is "X" otherwise it is "Y".

So looking back at the original "X" is

r0 ? "Z" : "M0"

This means if r0 is true then evaluate to "Z" otherwise evaluate to "M0"

And "Y" is

r0 ? "M" : "M"

which means if r0 is true then evaluate to "M" otherwise evaluate to "M" - this is actually pointless and Y could be placed with just "M", but that's beside the point.

Putting it together, if da>=d3_svg_arcMax and r0 is true then temp is "Z", but if r0 is false then temp is "M0". If da is not >=d3_svg_arcMax and r0 is true then temp is "M", but if r0 is false temp is "M"

To use parenthesis it would be like

var temp = (da >= d3_svg_arcMax ? (r0 ? "Z" : "M0") : (r0 ? "M" : "M"));