Js -数学运算

数学运算

括号运算 > 普通运算 > 赋值

1.任何数据类型的值加上字符串都是字符串

a = 'str' + null;console.log(a)a = 'str' + 2;console.log(a)a = 2 + 'str';console.log(a)a = 'str' + 1 + 1;console.log(a)a = 'str' + (1 + 1);console.log(a)运行结果：strnullstr22strstr11str2

        如下面代码段能够总结出，在进行/运算时，被除数和除数先进行Number类型转换时有一方结果为NAN，最终的结果为NAN。可以正常运算后除数为0,结果为infinity。0/0为NAN。Infinity和-Infinity以及NAN都为数字类型number。在进行%运算时，与/相似，不同的是%0的运算结果为NAN。-减运算先进行Number类型转换时有一方结果为NAN，最终的结果为NAN。

console.log(0/0)console.log(Number('34f'))console.log(typeof (Number('34f')))console.log('34f'/2)console.log(typeof ('34f'/2))console.log(Number([1, 4]))console.log(typeof (Number([1, 4])))console.log(2/[1])console.log(typeof (2/[1]))console.log([2,1]/2)console.log(typeof ([2,1]/2))console.log(-2/'0t')console.log(typeof (-2/'0t'))console.log('ds'/0)console.log(typeof ('ds'/0))console.log(1/0)console.log(typeof(1/0))console.log(-1/0)console.log(typeof(-1/0))运行结果：NaNNaNnumberNaNnumberNaNnumber2numberNaNnumberNaNnumberNaNnumberInfinitynumber-Infinitynumber console.log(0%0)console.log(Number('34f'))console.log(typeof (Number('34f')))console.log('34f'%2)console.log(typeof ('34f'%2))console.log(Number([1, 4]))console.log(typeof (Number([1, 4])))console.log(2%[1])console.log(typeof (2%[1]))console.log([2,1]%2)console.log(typeof ([2,1]%2))console.log(-2%'0t')console.log(typeof (-2%'0t'))console.log('ds'%0)console.log(typeof ('ds'%0))console.log(1%0)console.log(typeof(1%0))console.log(-1%0)console.log(typeof(-1%0))运行结果：NaNNaNnumberNaNnumberNaNnumber0numberNaNnumberNaNnumberNaNnumberNaNnumberNaNnumber

> <比较

number 和 string 比较 需要将string转为number,string 和 string比较从左到右比较两个字符串的字符ASCII码。

console.log(5>'6')console.log('4.5'>'11')运行结果：falsetrue

== 与 ===

==是不看数据类型，===是需要看数据类型是否相等

NAN是包括与自己在内的任何数据都不相等

console.log(NaN==NaN)console.log('1' == 1)console.log('1' === 1)运行结果：falsetruefalse