Read content from PDF using React Native - reactjs

Question

I am trying to read text from PDF file using expo and React Native. I used the below code to read but it's not working. On click of a button i use the DocumentPicker to select the PDF file and then i wanted to extract the text from the document alone. I am trying to create a app to read out the text for me.
But i am not able to do that. Thanks in advance.
loadText = async()=>{
//Alert.alert("load text triggered");
let result = await DocumentPicker.getDocumentAsync({});
if(result.type == 'success') {
// alert(result.uri);
let contents = await FileSystem.readAsStringAsync(result.uri);
//console.warn('content', contents);
if(contents.length > 0){
//let res = base64.fromByteArray(this.stringToUint8Array(contents));
//alert("t" + res);
this.setState({textToBeRead : this.atob(contents)});
alert("test" + this.state.textToBeRead);
}
}
};
atob = (input) => {
const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';
let str = input.replace(/=+$/, '');
let output = '';
if (str.length % 4 == 1) {
throw new Error("'atob' failed: The string to be decoded is not correctly encoded.");
}
for (let bc = 0, bs = 0, buffer, i = 0;
buffer = str.charAt(i++);
~buffer && (bs = bc % 4 ? bs * 64 + buffer : buffer,
bc++ % 4) ? output += String.fromCharCode(255 & bs >> (-2 * bc & 6)) : 0
) {
buffer = chars.indexOf(buffer);
}
return output;
}