sheet_to_json use lots of memory

i upload a 11 kb xlsx file and want to convert it to json in my server. my server only has 512mb memory, and i got node process killed when execute sheet_to_json method. the scripts works well in my pc which has 8gb memory. is sheet_to_json function use a lot of memory which is much bigger than file itself ? is there any tips to solve memory problems ? thanks

[SheetJSDev]

The root cause of the issue is a bad reported sheet size: If you unzip the file (XLSX is really a zip format) and look at the xml in xl/worksheets/sheet1.xml you’ll see:

  <dimension ref="A1:W1048576"/>
  <row r="1048576" customFormat="false" ht="12.8" hidden="false" customHeight="false" outlineLevel="0" collapsed="false"/>

The first line says that the file has over 1M records and the second line is completely unnecessary (guessing it was exported from a third party tool?)

Can you try overwriting the range using the update_sheet_range function from the wiki:

function update_sheet_range(ws) {
  var range = {s:{r:20000000, c:20000000},e:{r:0,c:0}};
  Object.keys(ws).filter(function(x) { return x.charAt(0) != "!"; }).map(XLSX.utils.decode_cell).forEach(function(x) {
    range.s.c = Math.min(range.s.c, x.c); range.s.r = Math.min(range.s.r, x.r);
    range.e.c = Math.max(range.e.c, x.c); range.e.r = Math.max(range.e.r, x.r);
  });
  ws['!ref'] = XLSX.utils.encode_range(range);
}

Call that function on the worksheet just before passing it to sheet_to_json. It scans the cells to recalculate the range.

[xiaoxiaodek]

It seems to be beter by using type Map; (node verison v14.9.0)

const process = require('process')
console.log('before', process.memoryUsage())
console.time('test')
// const o = {}
const o = new Map();
for (let R = 1; R <= 1048575; ++R) {
  for (let C = 0; C <= 22; ++C) {
    // o['!' + C + R];
    o.get('!' + C + R)
  }
}
console.timeEnd('test')
console.log('after', process.memoryUsage())

this may be helpful：

function sheet_to_json(_sheet, opts) {
	const sheet = new Map(Object.entries(_sheet))
	if(sheet == null || sheet.get("!ref") == null) return [];
	var val = {t:'n',v:0}, header = 0, offset = 1, hdr = [], v=0, vv="";
	var r = {s:{r:0,c:0},e:{r:0,c:0}};
	var o = opts || {};
	var range = o.range != null ? o.range : sheet.get("!ref");
	if(o.header === 1) header = 1;
	else if(o.header === "A") header = 2;
	else if(Array.isArray(o.header)) header = 3;
	else if(o.header == null) header = 0;
	switch(typeof range) {
		case 'string': r = safe_decode_range(range); break;
		case 'number': r = safe_decode_range(sheet.get("!ref")); r.s.r = range; break;
		default: r = range;
	}
	if(header > 0) offset = 0;
	var rr = encode_row(r.s.r);
	var cols = [];
	var out = [];
	var outi = 0, counter = 0;
	var dense = Array.isArray(sheet);
	var R = r.s.r, C = 0, CC = 0;
	if(dense && !sheet.get(R)) sheet.set(R, []);
	for(C = r.s.c; C <= r.e.c; ++C) {
		cols[C] = encode_col(C);
		val = dense ? sheet.get(R)[C] : sheet.get(cols[C] + rr);
		switch(header) {
			case 1: hdr[C] = C - r.s.c; break;
			case 2: hdr[C] = cols[C]; break;
			case 3: hdr[C] = o.header[C - r.s.c]; break;
			default:
				if(val == null) val = {w: "__EMPTY", t: "s"};
				vv = v = format_cell(val, null, o);
				counter = 0;
				for(CC = 0; CC < hdr.length; ++CC) if(hdr[CC] == vv) vv = v + "_" + (++counter);
				hdr[C] = vv;
		}
	}
	for (R = r.s.r + offset; R <= r.e.r; ++R) {
		var row = make_json_row(sheet, r, R, cols, header, hdr, dense, o);
		if((row.isempty === false) || (header === 1 ? o.blankrows !== false : !!o.blankrows)) out[outi++] = row.row;
	}
	out.length = outi;
	return out;
}

function make_json_row(sheet, r, R, cols, header, hdr, dense, o) {
	var rr = encode_row(R);
	var defval = o.defval, raw = o.raw || !Object.prototype.hasOwnProperty.call(o, "raw");
	var isempty = true;
	var row = (header === 1) ? [] : {};
	if(header !== 1) {
		if(Object.defineProperty) try { Object.defineProperty(row, '__rowNum__', {value:R, enumerable:false}); } catch(e) { row.__rowNum__ = R; }
		else row.__rowNum__ = R;
	}
	if(!dense || sheet.get(R)) for (var C = r.s.c; C <= r.e.c; ++C) {
		var val = dense ? sheet.get(R)[C] : sheet.get(cols[C] + rr);
		if(val === undefined || val.t === undefined) {
			if(defval === undefined) continue;
			if(hdr[C] != null) { row[hdr[C]] = defval; }
			continue;
		}
		var v = val.v;
		switch(val.t){
			case 'z': if(v == null) break; continue;
			case 'e': v = void 0; break;
			case 's': case 'd': case 'b': case 'n': break;
			default: throw new Error('unrecognized type ' + val.t);
		}
		if(hdr[C] != null) {
			if(v == null) {
				if(defval !== undefined) row[hdr[C]] = defval;
				else if(raw && v === null) row[hdr[C]] = null;
				else continue;
			} else {
				row[hdr[C]] = raw || (o.rawNumbers && val.t == "n") ? v : format_cell(val,v,o);
			}
			if(v != null) isempty = false;
		}
	}
	return { row: row, isempty: isempty };
}

reference link: node issue v8 issue