运算符+；=生成意外结果javascript

功能范围（开始、结束、st）{
var-arr=[]；
var计数器=启动；
虽然（counter我不确定您希望代码做什么，但是
counter+=st | | counter+1
相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

另一方面，
counter=counter+st | | counter+1
相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

所以它们做了完全不同的事情。我假设操作符的优先级会让你失望。
我不确定你希望代码做什么，但是
计数器+=st | |计数器+1
相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

另一方面，
counter=counter+st | | counter+1
相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

所以他们做了完全不同的事情。我假设操作符的优先级会把你甩了。
区别在于

counter += st || counter + 1;

意思与

counter = counter + (st || counter + 1);

而
counter=counter+st | | counter+1
表示
counter=（counter+st）| |（counter+1）


在您的示例中，代码
st
是
undefined
，因此循环有效地执行

counter += counter + 1;

每次，这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

因此，大型跳过


另一方面，在

counter = counter + st || counter + 1;

st
为
未定义
意味着
计数器+st
为
NaN
，该值为false，因此有效运行

counter = counter + 1;

这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

但是，这只是偶然发生的。如果使用不同的参数调用函数，例如：


功能范围（开始、结束、st）{
var-arr=[]；
var计数器=启动；
而（counter的区别在于

counter += st || counter + 1;

意思与

counter = counter + (st || counter + 1);

而
counter=counter+st | | counter+1
表示
counter=（counter+st）| |（counter+1）


在您的示例中，代码
st
是
undefined
，因此循环有效地执行

counter += counter + 1;

每次，这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

因此，大型跳过


另一方面，在

counter = counter + st || counter + 1;

st
为
未定义
意味着
计数器+st
为
NaN
，该值为false，因此有效运行

counter = counter + 1;

这相当于

counter += (st || (counter + 1));

if(st) {
    counter = counter + st;
}
else {
    counter = counter + counter + 1;
}

counter = (counter + st ) || (counter + 1);

if(counter + st) {
    counter = counter + st;
}
else {
    counter = counter + 1;
}

counter = counter * 2 + 1;

counter += 1;

但是，这只是偶然发生的。如果使用不同的参数调用函数，例如：


功能范围（开始、结束、st）{
var-arr=[]；
var计数器=启动；
虽然（如果您显示它给您的是什么，与您期望的是什么，计数器可能会有帮助，因为运算符优先级。@crayonstreamit假设在未提供
st
的情况下为计数器添加1，因为它将是未定义的，如果您显示它给您的是什么，与您期望的是什么，因为运算符优先级。@crayonstreamit假设添加。）1如果未提供
st
，则计数器，因为它将未定义