How do I read the file contents from SharePoint API?

Hello all,

I am having issues retrieving the values from my Sharepoint files. Currently, I am able to retrieve my file via Sharepoint but is there anyway that I can read my files content? (I have various file type such as xlsx, ppt, docx and pdf). I am not sure how I can retrieve the file contents?

http://www.test.com.sg/Shared Documents/docT.xlsx
http://www.test.com.sg/Shared Documents/docT.pdf
http://www.test.com.sg/Shared Documents/docT.docs
http://www.test.com.sg/Shared Documents/docT.ppt

This are part of the http://www.test.com.sg/Shared Documents/docT.xlsx 
```
0: {Key: 'Rank', Value: '17.5909175872803', ValueType: 'Edm.Double'}
1: {Key: 'DocId', Value: '83', ValueType: 'Edm.Int64'}
2: {Key: 'WorkId', Value: '83', ValueType: 'Edm.Int64'}
3: {Key: 'Title', Value: 'docT', ValueType: 'Edm.String'}
4: {Key: 'Author', Value: 'Jedrek Koh;s3002013', ValueType: 'Edm.String'}
5: {Key: 'Size', Value: '14455', ValueType: 'Edm.Int64'}
6: {Key: 'Path', Value: 'http://www.test.com.sg/Shared Documents/docT.xlsx', ValueType: 'Edm.String'}
7: {Key: 'Description', Value: null, ValueType: 'Null'}
```