【深入理解JS核心技术】12. 什么是一阶函数

const firstOrder = () => console.log("I am a first order function!");
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function sum(num1, num2) { 
 return num1 + num2; 
} 

console.log(sum(10, 10)); // 20 

let anotherSum = sum; 
console.log(anotherSum(10, 10)); // 20 

sum = null; 
console.log(anotherSum(10, 10)); // 20
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function foo() {} 
let bar = function() {}; 
let baz = () => {}; 

console.log(foo.name); // foo 
console.log(bar.name); // bar 
console.log(baz.name); // baz 
console.log((() => {}).name); //（空字符串）
console.log((new Function()).name); // anonymous
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function foo() { }
console.log(foo.bind(null).name); // bound foo
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let dog = {
 years: 1,
 get age() {
  return this.years;
 },
 set age(newAge) {
  this.years = newAge;
 }
}
let propertyDescriptor = Object.getOwnPropertyDescriptor(dog, 'age');
console.log(propertyDescriptor.get.name); // get age
console.log(propertyDescriptor.set.name); // set age
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console.log(Object.getOwnPropertyDescriptor(dog, 'years'))

VM2829:1 
{value: 1, writable: true, enumerable: true, configurable: true}
configurable: true
enumerable: true
value: 1
writable: true
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