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Secure context: This feature is available only in secure contexts (HTTPS), in some or all supporting browsers.
Experimental: This is an experimental technology
Check the Browser compatibility table carefully before using this in production.
The write() method of the NDEFReader interface attempts to write an NDEF message to a tag and returns a Promise that either resolves when a message has been written to the tag or rejects if a hardware or permission error is encountered. This method triggers a permission prompt if the "nfc" permission has not been previously granted.
write(message)
write(message, options)
message
The message to be written, either a string, an ArrayBuffer, a TypedArray, a DataView, or an array of records. A record has the following members:
data Optional
Contains the data to be transmitted, a string, an ArrayBuffer, a TypedArray, a DataView, or an array of nested records
encoding Optional
A string specifying the record's encoding.
id Optional
A developer-defined identifier for the record.
lang Optional
A valid language tag according to RFC 5646: Tags for Identifying Languages (also known as BCP 47).
mediaType Optional
A valid MIME type.
recordType
A string indicating the type of data stored in data. It must be one of the following values:
"absolute-url"
An absolute URL to the data.
"empty"
An empty NDEFRecord.
"mime"
A valid MIME type.
"smart-poster"
A smart poster as defined by the NDEF-SMARTPOSTER specification.
"text"
Text as defined by the NDEF-TEXT specification.
"unknown"
The record type is not known.
"URL"
A URL as defined by the NDEF-URI specification.
options Optional
An object with the following properties:
overwrite
A boolean value specifying whether or not existing records should be overwritten, if such exists.
signal Optional
An AbortSignal that allows the current write operation to be canceled.
A Promise that either resolves when a message has been written to the tag or rejects if a hardware or permission error is encountered.
This method doesn't throw exceptions; instead, it rejects the returned promise, passing a DOMException whose name is one of the following:
AbortError
The scan operation was aborted with the AbortSignal passed in the options argument.
NotAllowedError
The permission for this operation was rejected or overwrite is false and there are already records on the tag.
NotSupportedError
There is no NFC adapter compatible with Web NFC, or the available NFC adapter does not support pushing messages, or connection can not be established.
NotReadableError
The UA is not allowed to access underlying NFC adapter (e.g., due to user preference).
NetworkError
Transfer failed after it already started (e.g., the tag was removed from the reader).
The following example shows how to write a string to an NFC tag and process any errors that occur.
const ndef = new NDEFReader();
ndef
.write("Hello World")
.then(() => {
console.log("Message written.");
})
.catch((error) => {
console.log(`Write failed :-( try again: ${error}.`);
});
The following example shows how to write a record object (described above) to an NFC tag and process any errors that occur.
const ndef = new NDEFReader();
try {
await ndef.write({
records: [{ recordType: "url", data: "http://example.com/" }],
});
} catch {
console.log("Write failed :-( try again.");
}
It's sometimes useful to set a time limit on a write operation. For example, you ask the user to touch a tag, but no tag is found within a certain amount of time, then you time out.
const ndef = new NDEFReader();
ndef.onreading = (event) => console.log("We read a tag!");
function write(data, { timeout } = {}) {
return new Promise((resolve, reject) => {
const controller = new AbortController();
controller.signal.onabort = () =>
reject(new Error("Time is up, bailing out!"));
setTimeout(() => controller.abort(), timeout);
ndef.addEventListener(
"reading",
(event) => {
ndef.write(data, { signal: controller.signal }).then(resolve, reject);
},
{ once: true },
);
});
}
await ndef.scan();
try {
// Let's wait for 5 seconds only.
await write("Hello World", { timeout: 5_000 });
} catch (err) {
console.error("Something went wrong", err);
} finally {
console.log("We wrote to a tag!");
}
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