2.3 KiB
2.3 KiB
id, title, challengeType, isBeta
| id | title | challengeType | isBeta |
|---|---|---|---|
| 5d79253307ecd49e030bdcd1 | Part 023 | 0 | true |
Description
Recursion is when a function calls itself. We often use it instead of while/for loops, as loops usually involve mutable state.
Replace the empty string in highPrecedence with a call to highPrecedence with str2 as argument.
Instructions
Tests
tests:
- text: See description above for instructions.
testString: assert(highPrecedence("2*2*2") === "8" && highPrecedence("2*2") === "4" && highPrecedence("2+2") === "2+2");
Challenge Seed
<script>
const infixToFunction = {
"+": (x, y) => x + y,
"-": (x, y) => x - y,
"*": (x, y) => x * y,
"/": (x, y) => x / y
};
const infixEval = (str, regex) =>
str.replace(regex, (_, arg1, fn, arg2) =>
infixToFunction[fn](parseFloat(arg1), parseFloat(arg2))
);
const highPrecedence = str => {
const regex = /([0-9.]+)([*\/])([0-9.]+)/;
const str2 = infixEval(str, regex);
return str === str2 ? str : "";
};
</script>
Before Test
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Spreadsheet</title>
<style>
#container {
display: grid;
grid-template-columns: 50px repeat(10, 200px);
grid-template-rows: repeat(11, 30px);
}
.label {
background-color: lightgray;
text-align: center;
vertical-align: middle;
line-height: 30px;
}
</style>
</head>
<body>
<div id="container">
<div></div>
</div>
After Test
</body>
</html>
Solution
<script>
const infixToFunction = {
"+": (x, y) => x + y,
"-": (x, y) => x - y,
"*": (x, y) => x * y,
"/": (x, y) => x / y
};
const infixEval = (str, regex) =>
str.replace(regex, (_, arg1, fn, arg2) =>
infixToFunction[fn](parseFloat(arg1), parseFloat(arg2))
);
const highPrecedence = str => {
const regex = /([0-9.]+)([*\/])([0-9.]+)/;
const str2 = infixEval(str, regex);
return str === str2 ? str : highPrecedence(str2);
};
</script>