javascript - 如何写If/else语句？

Question

x = 1;    
if(x = 10) {x = 1;} 
else {x = x + 1;}
alert (x);

结果总是1，而不是1,2,3...

Answer 1

替换

if(x = 10) {x = 1;} 

与

if(x == 10) {x = 1;} 

因为 x=10 返回 10，它在测试中评估为 true，因此代码 {x = 1;} 是执行。

来自 the MDN about if...else :

Any value that is not undefined, null, 0, NaN, or the empty string (""), and any object, including a Boolean object whose value is false, evaluates to true when passed to a conditional statement