强制默认参数位于参数列表的最后一个。
const defaultValue = 0;
export function f1(a = defaultValue) {
return a;
}
export function f2(a: number, b = defaultValue) {
return a + b;
}
export function f3(a: number, b?: number) {
return b !== undefined ? a + b : a;
}
export function f4(a: number, b?: number, c = defaultValue) {
return b !== undefined ? a + b + c : a + c;
}
export function f5(a: number, b = defaultValue, c?: number) {
return c !== undefined ? a + c : a + b;
}