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在js里Number.MAX_VALUE代表能够表示的最大数值。如果超过这个数值就会出现Infinity,但是我下边的计算很难理解
(Number.MAX_VALUE+123)==Number.MAX_VALUE //true why? (Number.MAX_VALUE+Number.MAX_VALUE)==Number.MAX_VALUE //false why? console.log(5.3e-324) //5e-324 why?
谁理解这是为什么,能解释下么?
因为 123 太小,不足以改变高位数表达
因为 Number.MAX_VALUE 够大,足以改变高位数表达
5.3e-324 的 .3 过小
总结: js 在很多时候会难以保证浮点数计算精度,如 0.1 + 0.2 != 0.3 // true
一个亿加1,四舍五入之后还是一个亿,差不多一个道理。到不了那么精确的
应该只是一种数值的表示吧,如果减号与数字隔开是无法计算的
In the first example, you just increase your number by a really tiny number: 123 according to 1.79^308 is nothing. So you "lost" some precision: it does not change the number. In the second one, you exceed the max value, so your number is not a number anymore, it is Infinity.
In the first example, you just increase your number by a really tiny number: 123 according to 1.79^308 is nothing. So you "lost" some precision: it does not change the number.
In the second one, you exceed the max value, so your number is not a number anymore, it is Infinity.
by Mistalis from stackoverflowsomething about Number.MAX_VALUE
因为 123 太小,不足以改变高位数表达
因为 Number.MAX_VALUE 够大,足以改变高位数表达
5.3e-324 的 .3 过小
总结: js 在很多时候会难以保证浮点数计算精度,如 0.1 + 0.2 != 0.3 // true
![](http://img.php.cn/upload/image/000/000/000/8ce733f1306819b0fb33bd37bf813836-0.png)
一个亿加1,四舍五入之后还是一个亿,差不多一个道理。到不了那么精确的
应该只是一种数值的表示吧,如果减号与数字隔开是无法计算的
by Mistalis from stackoverflow
something about Number.MAX_VALUE
说白了就是浮点数精度问题!