5.typescript函数

函数格式

function 函数名(参数列表): 返回值类型 {
    函数体 ...
    [return 返回值;]
}

let 函数名 = function (参数列表): 返回值类型 {
    函数体 ...
    [return 返回值;]
};
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必选函数

function text(name: string, age: number): string {
    return `${name}${age}`;
}
console.log(text("林扬生", 24));
---
function text(name, age) {
    return "".concat(name).concat(age);
}
console.log(text("林扬生", 24));
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可选函数

function text(name: string, age?: number): string {
    return `${name}${age}`;
}
console.log(text("林扬生", 24));
console.log(text("林扬生"));
---
function text(name, age) {
    return "".concat(name).concat(age);
}
console.log(text("林扬生", 24));//林扬生24
console.log(text("林扬生"));//林扬生undefined
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默认函数

function text(name: string, age: number=24): string {
    return `${name}${age}`;
}
console.log(text("林扬生", 24));
console.log(text("林扬生"));
---
function text(name, age) {
    if (age === void 0) { age = 24; }
    return "".concat(name).concat(age);
}
console.log(text("林扬生", 24));//林扬生24
console.log(text("林扬生"));//林扬生24
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剩余函数

参数的类型确定而参数个数不确定

function sum(...result: number[]): number {
    let sum = 0;
    for (let i = 0; i < result.length; i++) {
        sum += result[i];
    }
    return sum;
}
console.log(sum(1, 2, 3, 4, 5));
---
function sum() {
    var result = [];
    for (var _i = 0; _i < arguments.length; _i++) {
        result[_i] = arguments[_i];
    }
    var sum = 0;
    for (var i = 0; i < result.length; i++) {
        sum += result[i];
    }
    return sum;
}
console.log(sum(1, 2, 3, 4, 5));//15
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箭头函数

function a() {
    console.log(0);
}
const b = () => {
    console.log(1);
}
a();b();
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