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Transformer.js
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Transformer.js
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// Generated by CoffeeScript 1.3.3
var Transformer, stream;
stream = require('stream');
/*
Transforming data
=================
Transformation may occur synchronously or asynchronously dependending
on the provided transform callback and its declared arguments length.
Callback are called for each line and its arguments are :
* data CSV record
* index Incremented counter
* callback Callback function to be called in asynchronous mode
Unless you specify the `columns` read option, `data` are provided
as arrays, otherwise they are objects with keys matching columns
names.
In synchronous mode, the contract is quite simple, you receive an array
of fields for each record and return the transformed record.
In asynchronous mode, it is your responsibility to call the callback
provided as the third argument. It must be called with two arguments,
the first one is an error if any, the second is the transformed record.
Transformed records may be an array, an associative array, a
string or null. If null, the record will simply be skipped. When the
returned value is an array, the fields are merged in order.
When the returned value is an object, it will search for
the `columns` property in the write or in the read options and
smartly order the values. If no `columns` options are found,
it will merge the values in their order of appearance. When the
returned value is a string, it is directly sent to the destination
source and it is your responsibility to delimit, quote, escape
or define line breaks.
Transform callback run synchronously:
csv()
.from('82,Preisner,Zbigniew\n94,Gainsbourg,Serge')
.to(console.log)
.transform(function(data, index){
return data.reverse()
});
// Executing `node samples/transform.js`, print:
// 94,Gainsbourg,Serge\n82,Preisner,Zbigniew
Transform callback run asynchronously:
csv()
.from('82,Preisner,Zbigniew\n94,Gainsbourg,Serge')
.to(console.log)
.transform(function(data, index, callback){
process.nextTick(function(){
callback(null, data.reverse());
});
});
// Executing `node samples/transform.js`, print:
// 94,Gainsbourg,Serge\n82,Preisner,Zbigniew
Transform callback returning a string:
csv()
.from('82,Preisner,Zbigniew\n94,Gainsbourg,Serge')
.to(console.log)
.transform(function(data, index){
return (index>0 ? ',' : '') + data[0] + ":" + data[2] + ' ' + data[1];
});
// Executing `node samples/transform.js`, print:
// 82:Zbigniew Preisner,94:Serge Gainsbourg
*/
Transformer = function(csv) {
this.csv = csv;
return this;
};
Transformer.prototype.__proto__ = stream.prototype;
/* no doc
`transformer(csv).transform(line)`
----------------------------------
Call a callback to transform a line. Called from the `parse` function on each
line. It is responsible for transforming the data and finally calling `write`.
*/
Transformer.prototype.transform = function(line) {
var column, columns, csv, done, finish, i, lineAsObject, sync, _i, _len;
csv = this.csv;
columns = csv.options.from.columns;
if (columns) {
if (csv.state.count === 0 && columns === true) {
csv.options.from.columns = columns = line;
return;
}
lineAsObject = {};
for (i = _i = 0, _len = columns.length; _i < _len; i = ++_i) {
column = columns[i];
lineAsObject[column] = line[i] || null;
}
line = lineAsObject;
}
finish = (function(line) {
if (csv.state.count === 1 && csv.options.to.header === true) {
csv.stringifier.write(csv.options.to.columns || columns);
}
csv.stringifier.write(line);
if (csv.state.transforming === 0 && this.closed === true) {
return this.emit('end', csv.state.count);
}
}).bind(this);
csv.state.count++;
if (this.callback) {
sync = this.callback.length !== 3;
csv.state.transforming++;
done = function(err, line) {
var isObject;
if (err) {
return csv.error(err);
}
isObject = typeof line === 'object' && !Array.isArray(line);
if (csv.options.to.newColumns && !csv.options.to.columns && isObject) {
Object.keys(line).filter(function(column) {
return columns.indexOf(column) === -1;
}).forEach(function(column) {
return columns.push(column);
});
}
csv.state.transforming--;
return finish(line);
};
if (sync) {
try {
return done(null, this.callback(line, csv.state.count - 1));
} catch (err) {
return done(err);
}
} else {
try {
return this.callback(line, csv.state.count - 1, function(err, line) {
return done(err, line);
});
} catch (_error) {}
}
} else {
return finish(line);
}
};
/* no doc
`transformer(csv).end()`
------------------------
A transformer instance extends the EventEmitter and
emit the 'end' event when the last callback is called.
*/
Transformer.prototype.end = function() {
if (this.closed) {
return this.csv.error(new Error('Transformer already closed'));
}
this.closed = true;
if (this.csv.state.transforming === 0) {
return this.emit('end');
}
};
module.exports = function(csv) {
return new Transformer(csv);
};
module.exports.Transformer = Transformer;