How to make a WAV file in Javascript.

makewav.js

var Wav = function(opt_params){
	
	/**
	 * @private
	 */
	this._sampleRate = opt_params && opt_params.sampleRate ? opt_params.sampleRate : 44100;
	
	/**
	 * @private
	 */
	this._channels = opt_params && opt_params.channels ? opt_params.channels : 2;  
	
	/**
	 * @private
	 */
	this._eof = true;
	
	/**
	 * @private
	 */
	this._bufferNeedle = 0;
	
	/**
	 * @private
	 */
	this._buffer;
	
};

Wav.prototype.setBuffer = function(buffer){
	this._buffer = this.getWavInt16Array(buffer);
	this._bufferNeedle = 0;
	this._internalBuffer = '';
	this._hasOutputHeader = false;
	this._eof = false;
};

Wav.prototype.getBuffer = function(len){
	
	var rt;
	if( this._bufferNeedle + len >= this._buffer.length ){
		rt = new Int16Array(this._buffer.length - this._bufferNeedle);
		this._eof = true;
	}
	else {
		rt = new Int16Array(len);
	}
	
	for(var i=0; i<rt.length; i++){
		rt[i] = this._buffer[i+this._bufferNeedle];
	}
	this._bufferNeedle += rt.length;
	
	return  rt.buffer;
	

};

Wav.prototype.eof = function(){
	return this._eof;
};

Wav.prototype.getWavInt16Array = function(buffer){
		
	var intBuffer = new Int16Array(buffer.length + 23), tmp;
	
	intBuffer[0] = 0x4952; // "RI"
	intBuffer[1] = 0x4646; // "FF"
	
	intBuffer[2] = (2*buffer.length + 15) & 0x0000ffff; // RIFF size
	intBuffer[3] = ((2*buffer.length + 15) & 0xffff0000) >> 16; // RIFF size
	
	intBuffer[4] = 0x4157; // "WA"
	intBuffer[5] = 0x4556; // "VE"
		
	intBuffer[6] = 0x6d66; // "fm"
	intBuffer[7] = 0x2074; // "t "
		
	intBuffer[8] = 0x0012; // fmt chunksize: 18
	intBuffer[9] = 0x0000; //
		
	intBuffer[10] = 0x0001; // format tag : 1 
	intBuffer[11] = this._channels; // channels: 2
	
	intBuffer[12] = this._sampleRate & 0x0000ffff; // sample per sec
	intBuffer[13] = (this._sampleRate & 0xffff0000) >> 16; // sample per sec
	
	intBuffer[14] = (2*this._channels*this._sampleRate) & 0x0000ffff; // byte per sec
	intBuffer[15] = ((2*this._channels*this._sampleRate) & 0xffff0000) >> 16; // byte per sec
	
	intBuffer[16] = 0x0004; // block align
	intBuffer[17] = 0x0010; // bit per sample
	intBuffer[18] = 0x0000; // cb size
	intBuffer[19] = 0x6164; // "da"
	intBuffer[20] = 0x6174; // "ta"
	intBuffer[21] = (2*buffer.length) & 0x0000ffff; // data size[byte]
	intBuffer[22] = ((2*buffer.length) & 0xffff0000) >> 16; // data size[byte]	

	for (var i = 0; i < buffer.length; i++) {
		tmp = buffer[i];
		if (tmp >= 1) {
			intBuffer[i+23] = (1 << 15) - 1;
		}
		else if (tmp <= -1) {
			intBuffer[i+23] = -(1 << 15);
		}
		else {
			intBuffer[i+23] = Math.round(tmp * (1 << 15));
		}
	}
	
	return intBuffer;
};
var i=0, vol=0.1,
    sampleRate = 48000, 
    wav = new Wav({sampleRate: sampleRate, channels: 1}),
    buffer = new Float32Array(sampleRate);

while(i<sampleRate){
    if( parseInt(i/100) % 2 ){
        buffer[i] = -vol;
    }
    else {
        buffer[i] = vol;
    }
    i++;
}
wav.setBuffer(buffer);

var srclist = [];
while( !wav.eof() ){
    srclist.push(wav.getBuffer(1000));
}

var b = new Blob(srclist, {type:'audio/wav'});
var URLObject = window.webkitURL || window.URL;
var url = URLObject.createObjectURL(b);
document.write("<a href='"+url+"'>play</a>");

There will be problem with URLObject if it runs on the client. I'm finding a workaround.

nice work ^_^
can i use some part of you code on my diploma in university?

In wav.getBuffer(1000) what is the use of 1000 ? I have tried changing its value, I see no difference.

Anyone has an idea how we would go about writing an INFO chunk with LIST sub-chunks containing song metadata? (e.g. artist name, track number, etc.)

@JohnWeisz have you found a way to do that yet? I'm trying to do the same thing.