What if a tooltip expects a position flag, but receives an answer flag whose value is also "right"? The function can mistake one identifier for the other. A namespace collision occurs when distinct names or values are confused; JavaScript Symbols can provide unique flags. section 13.1
Listing 13.1. Using constants as flags
const answer = {
CORRECT : 'right',
INCORRECT : 'wrong'
}
const positions = {
TOP : 'top',
BOTTOM : 'bottom',
LEFT : 'left',
RIGHT : 'right'
}
function addToolTip(content, position) {
switch(position) {
case positions.TOP:
// add content above
break;
case positions.BOTTOM:
// add content below
break;
case positions.RIGHT: 1
// add content to right
break;
case positions.LEFT:
// add content to left
break;
default:
throw new Error(`${position} is not a valid position`)
break;
}
}
addToolTip('You are not logged in', answer.CORRECT); 2
The answer and position objects use string values, so passing answer.CORRECT matches positions.RIGHT and selects the right-side case instead of reporting an error. section 13.1
Give each flag a unique Symbol
Set positions.RIGHT to Symbol('right'). Calling Symbol('right') again creates a different symbol, so a flag from another set will not match it merely because the descriptions are the same. section 13.1
