==与===的区别

==比较值是否相等,内部会进行强制类型转换

===比较值之前,会比较数据类型是否相等

若两个数值之间==结果为false,则===必为false. 

x	y	==	===
undefined	undefined	true	true
null	null	true	true
true	true	true	true
false	false	true	true
"foo"	"foo"	true	true
Symbol()	Symbol()	false	false
0	0	true	true
+0	-0	true	true
0	false	true	false
""	false	true	false
""	0	true	false
"0"	0	true	false
"17"	17	true	false
[1,2]	"1,2"	true	false
new String("foo")	"foo"	true	false
null	undefined	true	false
null	false	false	false
undefined	false	false	false
{ foo: "bar" }	{ foo: "bar" }	false	false
new String("foo")	new String("foo")	false	false
0	null	false	false
0	NaN	false	false
"foo"	NaN	false	false

转载于:https://www.cnblogs.com/fan-jing/p/7424433.html