Generate Encoded Polyline Algorithm Format for Google Static Maps API (JavaScript)

encodeGPolyline.js

//Generate Encoded Polyline Algorithm Format for Google Static Maps API
// http://bit.ly/sw3deL (Japanese)
// http://bit.ly/tnKt4m (English)

function encodeGPolyline(path){
	var enc = "";
	var old = true;
	for(c in path){
		var latlng = path[c];
		if(old === true){
			enc += encodeGPolylineNum(latlng[0])+
			       encodeGPolylineNum(latlng[1]);
		}else{
			enc += encodeGPolylineNum(latlng[0] - old[0])+
			       encodeGPolylineNum(latlng[1] - old[1]);
		}
		old = latlng;
	}
	return enc;
}

function encodeGPolylineNum(num){
	var fu = false;
	if(num < 0){
		fu = true;
	}
	//STEP2
	num = Math.round(num * 100000);
	//STEP3
	//STEP4
	num = num << 1;
	//STEP5
	if(fu){
			num = ~num;
	}
	//STEP6 - STEP7
	num = num.toString(2);
	var n = [];
	for(var c = 0; c < num.length; c++){
		n.push(num.charAt(c));
	}
	num = [];
	var nn = "";
	for(c=n.length-1;c >= 0;c--){
		nn = n[c] + nn;
		if(nn.length == 5){
			num.push(nn);
			nn = "";
		}
	}
	if(nn.length>0){
		nn = str_repeat("0",5 - nn.length) + nn;
		num.push(nn);
	}
	//STEP8 - STEP9 - STEP10 - STEP11
 
	for(var c = 0;c < num.length;c++){
		if(c != num.length - 1){
			num[c] = String.fromCharCode(bindec(num[c]) + 32 + 63);
		}else{
			num[c] = String.fromCharCode(bindec(num[c]) + 63);
		}
	}
	return num.join("");
}

function str_repeat(str, n){
    var ret = "";
    for (; n > 0; n >>>= 1, str += str) if (n & 1) ret += str;
    return ret;
}


function bindec(binary_string) {
    binary_string = (binary_string + '').replace(/[^01]/gi, '');
    return parseInt(binary_string, 2);
}

//例
console.log(encodeGPolylineNum(-179.9832104));
console.log(encodeGPolyline(
	[
		[38.5,-120.2],[40.7,-120.95],[43.252,-126.453]
	]
));