Currency: Round to number of significant figures instead of number of decimal places.

[tossj]

Description of new Instant Answer, or changes

Currently the Currency and Cryptocurrency IAs are rounding to a certain number of digits, instead of rounding to a certain number of significant figures. This causes conversions to be inaccurate.

For example, https://duckduckgo.com/?q=0.1+usd+to+eur&ia=currency currently gives 0.09 EUR, but should be giving 0.088 EUR. (Conversion as of Mid-Market Rates: 2018-12-08 at 17:00 UTC)

For the Cryptocurrency IA, https://duckduckgo.com/?q=1+ftc+to+usd&ia=cryptocurrency currently gives 0.02 USD, but should be giving 0.018 USD. (Conversion as of Market Rates: 2018-12-09 at 12:07 UTC)

This PR fixes these issues, and also fixes the issue in the inverse direction. It does so by replacing toFixed() with toPrecision(). toPrecision can sometimes return a number in its exponential format (e.g. 1200 = 1.2e+3), but the HTML5 input field with type number will display these correctly.

Related Issues and Discussions

Fixes #3537

People to notify

@moollaza

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Instant Answer Page: https://duck.co/ia/view/currency

[daxtheduck]

Currency Conversion

Description: Currency Convertor provided by XE.com

Example Query: convert 499 usd to cad, cad to usd, cny?

Tab Name: Currency

Source:

These are the important fields from the IA page. Please check these for errors or missing information and update the IA page

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This is an automated message which will be updated as changes are made to the IA page

[moollaza]

@pjhampton do you remember why we chose decimal places? I feel like it was it to prevent the strings from being too long?

[pjhampton]

@moollaza it seemed to be a search industry standard and a UX decision. However, I'm not opposed to this - just needs cross browser testing.

There was also an issue with firefox and using the number input type (reported by Andrey, if I remember correctly). This is why we didn't use a type="number" on the calculator either.