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【JavaScript

1、严格模式（每次写js之前都要写

//严格模式
'use  strict';

2、三种函数表达

1）函数声明

//计算年龄的函数，基于给定的出生年份
//函数声明  
//function 函数名（参数）{};
function calcAge1(birthYear) {return 2037 - birthYear;
}
const age1 = calcAge1(1991);
console.log(age1); //输出46

2）匿名函数

//匿名函数
//函数表达式  
//变量类型 名称 = function(参数){};
const calcAge2 = function (birthYear) {return 2037 - birthYear;
}
const age2 = calcAge2(1991);
console.log(age1);

3）箭头函数

//箭头函数
//变量类型 名称 = (参数) =>{方法};
const calcAge3 = birthYear => 2037 - birthYear;
const age3 = calcAge3(1991);
console.log(age3);//退休
const yearsUntilRetiremet = (birthYear, firstName) => {const age = 2037 - birthYear;const retirement = 65 - age;return `${firstName} retires in ${retirement} years`;
}console.log(yearsUntilRetiremet(1991, 'Jonas')); //还有19年退休
console.log(yearsUntilRetiremet(1980, 'Bobs'));

3、从函数中调用另一个函数

//从函数内部调用另一个函数
const cutPieces = function (fruit) {return fruit * 4;
};const fruitProcessor = function (apples, oranges) {const applPieces = cutPieces(apples);const orangesPieces = cutPieces(oranges);const juice = `Juice with ${applPieces} pieces of apple and ${orangesPieces} pieces of orange.`return juice;
};console.log(fruitProcessor(2, 3)); //2*4=8   3*4=12
const calcAge = function (birthYear) {return 2037 - birthYear;
};const yearsUntilRetiremet = function (birthYear, firstName) {const age = calcAge(birthYear); //调用calcAge，获得年龄const retirement = 65 - age;if (retirement > 0) {console.log(`${firstName} retires in ${retirement} years`);return retirement;} else {console.log(`${firstName} has already retired`);return -1;}
};console.log(yearsUntilRetiremet(1991, "Jonas"));
console.log(yearsUntilRetiremet(1970, "MARK"));

本文标签： javascript

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