TS语法校验常见错误

• property does not exist on type Object
  • 复现
  • 解决
• Expression of type ‘string’ can’t be used to index type
  • 复现
  • 解决
• BMW WARNING

property does not exist on type Object

复现

Property ‘length’ does not exist on type’Object’.

var obj: Object = Object.create(null);
obj.value = "value"; //[ts] Property 'length' does not exist on type'Object'.

解决

将对象类型设置为 any

var obj: any = Object.create(null);
obj.value = "value";

通过字符方式获取对象属性

var obj: Object = Object.create(null);
obj["value"] = "value";

通过接口定义对象所具有的属性

var obj: ValueObject = Object.create(null);
obj.value = "value";

interface ValueObject {
  value?: string;
}

使用断言强制执行

var obj: Object = Object.create(null);
(obj as any).value = "value"

Expression of type ‘string’ can’t be used to index type

复现

Element implicitly has an ‘any’ type because expression of type ‘string’ can’t be used to index type

person 并未明确指定键值类型（即隐式指定为任意类型），任意类型与 getValue 传参的 string 类型冲突。

const person = {
  name: "sk",
  age: 22,
};

function getValue(arg: string) {
  return person[arg]; // Element implicitly has an 'any' type because expression of type 'string' can't be used to index type '{ name: string; age: number; }'.
}

解决

tsconfig.json

tsconfig.json中配置suppressImplicitAnyIndexErrors: true

定义接口

const person = {
    name: 'sk',
    age: 22
};

function getValue(arg: string) {
	interface IPerson {
		[key: string]: any
	}
    return (<IPerson>person)[arg];
}

BMW WARNING

• Bulletin

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• Material

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• Warrant

本文作者： Skyline(lty)
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