今天小编给大家分享一下JavaScript怎么验证API的相关知识点，内容详细，逻辑清晰，相信大部分人都还太了解这方面的知识，所以分享这篇文章给大家参考一下，希望大家阅读完这篇文章后有所收获，下面我们一起来了解一下吧。
约束验证 DOM 方法
| Property | Description |
|---|---|
| checkValidity() | Returns true if an input element contains valid data. |
| setCustomValidity() | Sets the validationMessage property of an input element. |
如果输入字段包含无效数据，则显示一条消息：
checkValidity() 方法
<input id="id1" type="number" min="100" max="300" required><button onclick="myFunction()">OK</button><p id="demo"></p><script>function myFunction() { const inpObj = document.getElementById("id1"); if (!inpObj.checkValidity()) { document.getElementById("demo").innerHTML = inpObj.validationMessage; }}</script>约束验证 DOM 属性
| Property | Description |
|---|---|
| validity | Contains boolean properties related to the validity of an input element. |
| validationMessage | Contains the message a browser will display when the validity is false. |
| willValidate | Indicates if an input element will be validated. |
有效性属性
输入元素的有效性属性包含许多与数据有效性相关的属性：
| Property | Description |
|---|---|
| customError | Set to true, if a custom validity message is set. |
| patternMismatch | Set to true, if an element's value does not match its pattern attribute. |
| rangeOverflow | Set to true, if an element's value is greater than its max attribute. |
| rangeUnderflow | Set to true, if an element's value is less than its min attribute. |
| stepMismatch | Set to true, if an element's value is invalid per its step attribute. |
| tooLong | Set to true, if an element's value exceeds its maxLength attribute. |
| typeMismatch | Set to true, if an element's value is invalid per its type attribute. |
| valueMissing | Set to true, if an element (with a required attribute) has no value. |
| valid | Set to true, if an element's value is valid. |
例子
如果输入字段中的数字大于 100(输入的max 属性)，则显示一条消息：
rangeOverflow 属性
<input id="id1" type="number" max="100"><button onclick="myFunction()">OK</button><p id="demo"></p><script>function myFunction() { let text = "Value OK"; if (document.getElementById("id1").validity.rangeOverflow) { text = "Value too large"; }}</script>如果输入字段中的数字小于 100(输入的min属性)，则显示一条消息：
rangeUnderflow 属性
<input id="id1" type="number" min="100"><button onclick="myFunction()">OK</button><p id="demo"></p><script>function myFunction() { let text = = "Value OK"; if (document.getElementById("id1").validity.rangeUnderflow) { text = "Value too small"; }}</script>以上就是“JavaScript怎么验证API”这篇文章的所有内容，感谢各位的阅读！相信大家阅读完这篇文章都有很大的收获，小编每天都会为大家更新不同的知识，如果还想学习更多的知识，请关注编程网行业资讯频道。
