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77 lines
2.3 KiB
77 lines
2.3 KiB
# Bit Masks
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**Tier:** 2-Intermediate
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It's difficult to find an app that doesn't rely on some form of conditional
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logic to implement its functionality. This is almost always performed using
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statements like:
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```
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if (processAccount === true) {
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/* do something */
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}
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```
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If and switch statements work well for a limited number of conditionals, but
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what if your app had 10's or 100's of conditionals to evaluate? Luckily, there's
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another way.
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The goal of the Bit Masks app is demonstrate how to use bit masks to evaluate
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longer sequences of switches without having to rely on long strings of
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conditional statements.
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## User Stories
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- [ ] User can see a vertical list of checkboxes with the following cities
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and their timezones:
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- Moscow: GMT +3
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- Paris: GMT +2
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- Berlin: GMT +2
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- Brussels: GMT +2
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- Amsterdam: GMT +2
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- Rome: GMT +2
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- London: GMT +1
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- Dublin: GMT +1
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- New York: GMT -4
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- Washington, DC: GMT -4
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- St. Louis: GMT -5
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- Los Angeles: GMT -7
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- Tokyo: GMT +9
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- Beijing: GMT +8
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- Ho Chi Mihn City: GMT +7
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- Mumbai: GMT +5
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- [ ] User can see a GMT search box where an integer representing a GMT offset
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can be entered into and a 'Find Cities' button.
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- [ ] User can click the 'Find Cities' button to display the names of the
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cities in that GMT offset in an output area.
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### Developer Notes
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For this exercise the developer should use sequences of 24
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binary bits, each corresponding a GMT time zone from +12 to -12 to map cities
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to their timezones.
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Searches should be conducted by combining a bit mask for the desired time zone
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against the city-specific bit sequences to identify matches. Determining if a
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city meets the search criteria shouldn't rely on a statement such as
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```
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if (city[i].gmtOffset === searchOffset ) {
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/* Found it! */
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}
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```
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It should instead rely on a bitwise operation.
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## Bonus features
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- [ ] User can search for cities NOT in the GMT offset entered in the
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search box.
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- [ ] User can see a summary count of the number of cities that met the
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search criteria.
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## Useful links and resources
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- [World Time Zones](https://greenwichmeantime.com/time-zone/definition/)
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- [Bitwise Operators (MDN)](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Bitwise_Operators)
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## Example projects
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[Bitwise Operation](https://codepen.io/Lunoware/pen/VBZgQd)
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