The magical _javascript skill of JS and operator and OR operator

If the following question is implemented under different conditions (add_step changes), the add_level result values are different:

Copy Code code as follows:

var add_level = 0;
if (Add_step = = 5) {
Add_level = 1;
}
else if (Add_step = 10) {
Add_level = 2;
}
else if (Add_step = 12) {
Add_level = 3;
}
else if (Add_step = 15) {
Add_level = 4;
}
else {
Add_level = 0;
}

1 The above functions can also be implemented by switch:

Copy Code code as follows:

var add_level = 0;
Switch (add_step) {
Case 5:add_level = 1;
Break
Case 10:add_level = 2;
Break
Case 12:add_level = 3;
Break
Case 15:add_level = 4;
Break
Default:add_level = 0;
Break

2) Javasctipt through | | and && to achieve:

Copy Code code as follows:

var add_level = (add_step==5 && 1) | | (add_step==10 && 2) | | (add_step==12 && 3) | | (add_step==15 && 4) | | 0;

3) The 2nd way of writing can also be abbreviated as:

Copy Code code as follows:

var add_level={' 5 ': 1, ' Ten ': 2, ' ': 3, ': 4}[add_step] | | 0;

A basic formula can be drawn from the 2nd way:

Copy Code code as follows:

Add_step==5 && add_level=1

Equivalent to <==>

Copy Code code as follows:

if (add_step==5) {

Add_level = 1

}