How to use input in js

In JS, the element is used to collect user input and can be operated and processed in the following ways: Attribute operations: get or set value (value), prompt information (placeholder), input type (type ). Event handling: capturing focus (focus), losing focus (blur), content change (input). Other methods: add event listener (addEventListener), remove event listener (removeEventListener), select input box text (select).

##Usage of elements in JS

< The input> element is a form element in HTML used to collect user input. JS allows developers to manipulate and process this element.

Attribute operation

• value: Get or set the value in the input box.
• placeholder: Set the prompt information in the input box.
• type: Specify the type of input box, such as text, number or password.

Event handling

• focus: Triggered when the input box gains focus.
• blur: Triggered when the input box loses focus.
• input: Triggered when the content of the input box changes.

Other methods

• addEventListener: Add an event listener for the input box.
• removeEventListener: Remove the event listener.
• select: Select the text in the input box.

Example

Get the value of the input box:

const inputValue = document.getElementById("myInput").value;

Set the prompt message when the input box gets focus:

document.getElementById("myInput").addEventListener("focus", () => {
  document.getElementById("myInput").placeholder = "请输入内容";
});

Check validity when the input box loses focus:

document.getElementById("myInput").addEventListener("blur", () => {
  if (isNaN(document.getElementById("myInput").value)) {
    alert("请输入数字");
  }
});

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