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Learning Exercise
With a while loop, you can execute code repeatably as long as a certain condition is fulfilled.
It is written with the while keyword followed by a condition wrapped in round brackets and a code block that contains the body of the loop wrapped in curly brackets.
while (condition) {
// code that is executed repeatedly as long as the condition is true
}
JavaScript also has a do-while loop. Here the condition is checked after the loop body was executed. This is useful when the condition depends on evaluations done in the body.
do {
// The code here will always be executed once and then
// repeatedly while the condition is true.
} while (condition);
Inside a loop body, you can use the break keyword to stop the execution of the loop entirely.
In contrast to this, the keyword continue only stops the execution of the current iteration and continues with the next one.
With continue you can often avoid wrapping big parts of the loop body in an if-statement.
let i = 0;
while (i < 100) {
i = i + 2;
if (i % 3 === 0) {
continue;
}
// The code here will only be executed when i was not divisible
// by 3 in the check above.
}
Besides the if-statement, JavaScript also has a switch-statement to conditionally execute logic.
It is used when a single variable needs to be compared to multiple variants.
The comparison is done by checking for strict equality (===), see concept comparison.
For some variable x, the switch statement in JavaScript has the following syntax.
switch (x) {
case option1:
// code that is executed when "x === option1" is true
break;
case option2:
// code that is executed when "x === option2" is true
break;
default:
// code that is executed when x does not equal any of the options
}
The default case is optional and used in case you want to execute some code if none of the other options match the variable.
The break statements above are needed because by default all cases are "fallthrough" in JavaScript.
That means without any break statement all the code in the cases below the first matching option would be executed even though x did not match those options.
This "fallthrough by default" behavior is a common pitfall when using switch in JavaScript.
Inside a function, return can also be used instead of break to avoid this problem.
Your friend Li Mei runs a juice bar where she sells delicious mixed fruit juices. You are a frequent customer in her shop and realized you could make your friend's life easier. You decide to use your coding skills to help Li Mei with her job.
Li Mei likes to tell her customers in advance how long they have to wait for a juice from the menu that they ordered.
She has a hard time remembering the exact numbers because the time it takes to mix the juices varies.
'Pure Strawberry Joy' takes 0.5 minutes, 'Energizer' and 'Green Garden' take 1.5 minutes each, 'Tropical Island' takes 3 minutes and 'All or Nothing' takes 5 minutes.
For all other drinks (e.g., special offers) you can assume a preparation time of 2.5 minutes.
To help your friend, write a function timeToMixJuice that takes a juice from the menu as an argument and returns the number of minutes it takes to mix that drink.
timeToMixJuice('Tropical Island');
// => 3
timeToMixJuice('Berries & Lime');
// => 2.5
A lot of Li Mei's creations include lime wedges, either as an ingredient or as part of the decoration. So when she starts her shift in the morning she needs to make sure the bin of lime wedges is full for the day ahead.
Implement the function limesToCut which takes the number of lime wedges Li Mei needs to cut and an array representing the supply of whole limes she has at hand.
She can get 6 wedges from a 'small' lime, 8 wedges from a 'medium' lime and 10 from a 'large' lime.
She always cuts the limes in the order in which they appear in the list, starting with the first item.
She keeps going until she reached the number of wedges that she needs or until she runs out of limes.
Li Mei would like to know in advance how many limes she needs to cut.
The limesToCut function should return the number of limes to cut.
limesToCut(25, ['small', 'small', 'large', 'medium', 'small']);
// => 4
Li Mei always works until 3pm. Then her employee Dmitry takes over. There are often drinks that have been ordered but are not prepared yet when Li Mei's shift ends. Dmitry will then prepare the remaining juices.
To make the hand-over easier, implement a function remainingOrders which takes the number of minutes left in Li Mei's shift and an array of juices that have been ordered but not prepared yet.
The function should return the orders that Li Mei cannot start preparing before the end of her workday.
The time left in the shift will always be greater than 0. The array of juices to prepare will never be empty. Furthermore, the orders are prepared in the order in which they appear in the array. If Li Mei starts to mix a certain juice, she will always finish it even if she has to work a bit longer. If there are no remaining orders left that Dmitry needs to take care of, an empty array should be returned.
remainingOrders(5, ['Energizer', 'All or Nothing', 'Green Garden']);
// => ['Green Garden']
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