英文:
javascript how to express many-digit exponentials to 2 decimal places
问题
我有一个JavaScript程序，它在控制台中输出形如'3.173538947635389377E+98'的大数组，经过尝试未能成功将它们缩减为类似'3.17E+98'的形式以便比较。
我将数字转换成字符串，计算小数点和E的位置，然后对字符串进行切割和处理，最终将其变为'317.35E+96'这种形式，其中96是3的倍数。然后，当我使用Number()重新表示为数字时，它又变回了'3.173538947635389377E+98'。
我本可以将它保留为字符串，但后续可能需要重新转换为数字。是否有简单的方法来降低复杂性？当字符串如此之长时，几乎不可能检查和找到相似的数字等。我猜JavaScript的开发人员有他们的原因，但我已经束手无策了。
英文:
I have a javascript program which spits out large arrays of numbers of the form '3.173538947635389377E+98', in the console, and have tried without luck to reduce them to something like '3.17E+98' for ease of comparison.
I Stringified the number, calculated the period and E locations, cut and diced until I had it of the string form '317.35E+96', with 96 as a multiple of 3.
Then when I re-expressed as a number using Number(), it reverted to '3.173538947635389377E+98'.
I could have left it as a string, but then would have to reconvert to Number later on.
Is there a simple way of reducing the complexity? It is nearly impossible to inspect and see similar numbers etc, when the strings are so long. I guess the js people have their reasons, but am at my wits end.
答案1
得分: 2
你可以使用 Intl.NumberFormat 与 engineering 记法：
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
const display = (n) => new Intl.NumberFormat('en', {
notation: 'engineering',
maximumFractionDigits: 2
}).format(n);
console.log(display(3.173538947635389377E+98));
<!-- end snippet -->
英文:
You can use Intl.NumberFormat with engineering notation:
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-js -->
const display = (n) => new Intl.NumberFormat('en', {
notation: 'engineering',
maximumFractionDigits: 2
}).format(n);
console.log(display(3.173538947635389377E+98));
<!-- end snippet -->
答案2
得分: 1
你可以使用 toFixed() 方法将多位数的指数表示为小数点后两位。
例如，
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var num = 3.14159265358979323846264338327950;
var result = num.toFixed(2);
document.getElementById("demo").innerHTML = result;
</script>
</body>
</html>
// 结果将是 3.14
英文:
You can use the toFixed() method to express many-digit exponentials to two decimal places.
For example,
<!-- begin snippet: js hide: false console: true babel: false -->
<!-- language: lang-html -->
<!DOCTYPE html>
<html>
<body>
<p id="demo"></p>
<script>
var num = 3.14159265358979323846264338327950;
var result = num.toFixed(2);
document.getElementById("demo").innerHTML = result;
</script>
</body>
</html>
<!-- end snippet -->
// result will be 3.14
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