匿名函数

匿名函数与函数声明有点不同。 当一个函数出现在 TypeScript 可以确定如何调用它的地方时,该函数的参数会自动被赋予类型。

Anonymous functions are a little bit different from function declarations. When a function appears in a place where TypeScript can determine how it's going to be called, the parameters of that function are automatically given types.

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// No type annotations here, but TypeScript can spot the bug
const names = ["Alice", "Bob", "Eve"];

// Contextual typing for function
names.forEach(function (s) {
  console.log(s.toUppercase());
});

// Contextual typing also applies to arrow functions
names.forEach((s) => {
  console.log(s.toUppercase());
});

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