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Improve|Improve Nested Conditionals（优化嵌套的条件语句） 面对大量的if-else语句
//method1
if (color) {
if (color === 'black') {
printBlackBackground();
} else if (color === 'red') {
printRedBackground();
} else if (color === 'blue') {
printBlueBackground();
} else if (color === 'green') {
printGreenBackground();
} else {
printYellowBackground();
}
} //method2
switch(color) {
case 'black':
printBlackBackground();
break;
case 'red':
printRedBackground();
break;
case 'blue':
printBlueBackground();
break;
case 'green':
printGreenBackground();
break;
default:
printYellowBackground();
} //method3
switch(true) {
case (typeof color === 'string' && color === 'black'):
printBlackBackground();
break;
case (typeof color === 'string' && color === 'red'):
printRedBackground();
break;
case (typeof color === 'string' && color === 'blue'):
printBlueBackground();
break;
case (typeof color === 'string' && color === 'green'):
printGreenBackground();
break;
case (typeof color === 'string' && color === 'yellow'):
printYellowBackground();
break;
} //method4
var colorObj = {
'black': printBlackBackground,
'red': printRedBackground,
'blue': printBlueBackground,
'green': printGreenBackground,
'yellow': printYellowBackground
};
if (color in colorObj) {
colorObj[color]();
}
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