Getting Started

Download and Installation

Relevant Resources

• COS XML JS SDK source code: Download here.
• Demo: Download here.

Preparing the Environment

1. JavaScript SDK requires the browser to support basic HTML5 features (IE 10 and higher) for AJAX file upload and MD5 checksum calculation.
2. Log in to the COS Console, create a bucket, and get the bucket name and region name.
3. Log in to the CAM Console and get the SecretId and SecretKey of your project.
4. Configure CORS rule. Put in * for AllowHeader. For ExposeHeaders, put in ETag, Content-Length, and other header fields JS needs to read as shown below. For more information, see Setting Cross-Origin Resource Sharing.
   

For the definitions of SecretId, SecretKey, Bucket and other terms, see COS Glossary.

Installing the SDK

You can install the SDK in the following ways:

Importing via script

<script src="./cos-auth.min.js"></script>

When the script tag references the SDK, the SDK occupies the global variable name COS, and its constructor can create an SDK instance.

Importing via webpack

Installing the SDK dependencies by running npm i cos-js-sdk-v5 --save supports webpack packaging scenarios. You can use NPM import as a module with the following code:

var COS = require('cos-js-sdk-v5');

Getting Started

Getting a Temporary Key

If the key is placed on the frontend, the SecretId and SecretKey will be exposed; therefore, we put the permanent key on the backend, and the frontend gets a temporary key from the backend through AJAX. In actual deployment, please add an additional authentication step of your website on the backend. For more information, see Generating and Using Temporary Keys.

Initialization

1. Create a web.html file, enter the following code, and modify the bucket name and region in web.html.
2. Deploy the temporary key service on the backend and modify the key service address in getAuthorization.
3. Place the web.html file on the web server, visit the page in a browser, and test file upload. The sample code for web.html is as follows:

<input id="file-selector" type="file">
<script src="dist/cos-js-sdk-v5.min.js"></script>
<script>
var Bucket = 'examplebucket-1250000000';
var Region = 'ap-beijing';

// Initialize an instance
var cos = new COS({
    getAuthorization: function (options, callback) {
        // Get a temporary key asynchronously
        $.get('http://example.com/server/sts.php', {
            bucket: options.Bucket,
            region: options.Region,
        }, function (data) {
            var credentials = data.credentials;
            callback({
                 TmpSecretId: credentials.tmpSecretId, 
                 TmpSecretKey: credentials.tmpSecretKey, 
                 XCosSecurityToken: credentials.sessionToken, 
                 ExpiredTime: data.expiredTime
            });
        });
    }
});

// The COS instance can then be used to call a COS request
// TODO

</script>

Configuration Items

Usage Examples

Create a COS SDK instance in one of the following ways:

• Method 1 (recommended): The backend gets a temporary key and sends it to the frontend for signature calculation.

  var COS = require('cos-js-sdk-v5');
  var cos = new COS({
    // Required parameters
    getAuthorization: function (options, callback) {
        // Server-side JS and PHP sample: https://github.com/tencentyun/cos-js-sdk-v5/blob/master/server/
        // For examples of other server-side programming languages, see COS STS SDK: https://github.com/tencentyun/qcloud-cos-sts-sdk
        // For the STS documentation, visit https://cloud.tencent.com/document/product/436/14048
        $.get('http://example.com/server/sts.php', {
            // The required parameters can be obtained from options
        }, function (data) {
            callback({
                TmpSecretId: data.TmpSecretId,
                TmpSecretKey: data.TmpSecretKey,
                XCosSecurityToken: data.XCosSecurityToken,
                ExpiredTime: data.ExpiredTime, // The SDK will not call getAuthorization again before the ExpiredTime time
            });
        });
    }
  });

• Method 2 (recommended): The permissions are controlled in a fine-grained manner. The backend gets a temporary key and sends it to the frontend. The frontend only reuses the key for the same request, and the backend can manage the permissions in a fine-grained manner through Scope.

  var COS = require('cos-js-sdk-v5');
  var cos = new COS({
    // Required parameters
    getAuthorization: function (options, callback) {
        // Server-side sample: https://github.com/tencentyun/qcloud-cos-sts-sdk/edit/master/scope.md
        $.ajax({
            method: 'POST',
            url: ' http://example.com/server/sts-scope.php',
            data: JSON.stringify(options.Scope),
            beforeSend: function () {
                xhr.setRequestHeader('Content-Type', 'application/json');
            },
            dataType: 'json',
            success: function (data) {
                var credentials = data.credentials;
                callback({
                    TmpSecretId: credentials.tmpSecretId,
                    TmpSecretKey: credentials.tmpSecretKey,
                    XCosSecurityToken: credentials.sessionToken, // sessionToken needs to be passed to XCosSecurityToken 
                    ExpiredTime: data.expiredTime,
                    ScopeLimit: true, // You need to set the fine-grained permission control to true to make sure that the key will only be reused for the same request
                });
            }
        });
    }
  });

• Method 3 (not recommended): The frontend needs to get a signature through getAuthorization before each request, and the backend uses a permanent or temporary key to calculate the signature and returns it to the frontend. This method will make it difficult for you to control the permission of multipart upload and thus is not recommended.

  var cos = new COS({
    // Required parameters
    getAuthorization: function (options, callback) {
        // The server obtains a signature. For more information, see the COS SDK for the corresponding programming language: https://cloud.tencent.com/document/product/436/6474
        // Note: There is a security risk. The backend needs to strictly control the permissions through method and pathname, such as prohibiting put /
        $.get('http://example.com/server/auth.php', {
            method: options.Method,
            pathname: '/' + options.Key,
        }, function (data) {
            callback({
                Authorization: data.authorization,
                // XCosSecurityToken: data.sessionToken, // If a temporary key is used, sessionToken needs to be passed to XCosSecurityToken
            });
        });
    },
    // Optional parameters
    FileParallelLimit: 3,    // Limit the number of concurrent file uploads
    ChunkParallelLimit: 3,   // Limit the number of concurrent part uploads when using multipart upload for a single file
    ProgressInterval: 1000,  // Limit the interval of upload onProgress callbacks
  });

• Method 4 (not recommended): The frontend uses a fixed key to calculate the signature. This method can be used for frontend debugging, but be sure to avoid key disclosure.

  var cos = new COS({
    SecretId: 'COS_SECRETID',
    SecretKey: 'COS_SECRETKEY',
  });

Parameters of the constructor

getAuthorization Callback Function (Using Method 1)

getAuthorization: function(options, callback) { ... }

getAuthorization Callback Parameters

After the temporary key is obtained, the callback returns an object. The attributes of the returned object are as shown below:

getAuthorization Callback Function (Using Method 2)

getAuthorization: function(options, callback) { ... }

getAuthorization Callback Parameters

After the getAuthorization calculation is completed, the callback returns a signature string or an object:
If a signature string is returned, the string is the credential field "Authorization" in the authentication header to be used by the request.
If an object is returned, the attributes of the object are as shown below:

Getting an Authentication Credential

There are three ways to obtain an authentication credential for the instance:

1. During instantiation, pass in the SecretId and SecretKey. Every time a signature is required, it will be internally calculated by the instance.
2. During instantiation, pass in the getAuthorization callback. Every time a signature is required, it will be calculated and returned to the instance through this callback.
3. During instantiation, pass in the getAuthorization callback. When the callback is called, a temporary key will be returned. After the key expires, the callback will be called again.

Below are some examples of common APIs. For more detailed initialization methods, see the examples in the demo.

Uploading an Object

The simple upload API can be used to upload small files. For large files, use the multipart upload API. For more information, see Object Operations.

document.getElementById('file-selector').onchange = function () {
    var file = this.files[0];
    if (!file) return;
    cos.putObject({
        Bucket: 'examplebucket-1250000000',
        Region: 'ap-beijing',
        Key: 'destination path/' + file.name,
    }, function (err, data) {
        console.log(err || data);
    });
});

Querying the Object List

cos.getBucket({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Prefix: 'exampledir/', // Pass in the prefix of files to be listed here
}, function (err, data) {
    console.log(err || data.Contents);
});

Downloading an Object

This API is used to read the object content. If you need to launch a browser to download the file, you can get the URL through cos.getObjectUrl and then start a download in the browser. For more information, see Pre-signed URL.

cos.getObject({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: 'exampleobject.txt',
}, function (err, data) {
    console.log(err || data.Body);
});

Deleting an Object

cos.deleteObject({
    Bucket: 'examplebucket-1250000000',
    Region: 'ap-beijing',
    Key: 'picture.jpg',
}, function (err, data) {
    console.log(err || data);
});