ssssssss-team/spider-flow · error · TypeError

this is null or not defined

Error message

this is null or not defined

What it means

formSelects-v4.js installs a polyfill for Array.prototype.forEach when it is missing. The polyfill follows the ES5 spec: if forEach is invoked on a null or undefined `this` (e.g. called on a variable that is null), it throws TypeError('this is null or not defined').

Solutions

1. Ensure the value is an array before calling forEach (initialize arrays, guard API/DOM results).
2. Modernize target browsers or ensure the native Array.prototype.forEach exists so the polyfill path isn't hit.
3. Use Array.isArray checks or default values (`(arr || []).forEach(...)`) before iteration.

Example fix

// before
items.forEach(function(item){ ... }); // items may be null
// after
(items || []).forEach(function(item){ ... });

if (!Array.isArray(items)) { items = items == null ? [] : [].concat(items); }

function asArray(v) { return Array.isArray(v) ? v : (v == null ? [] : Array.prototype.slice.call(v)); }

try {
  items.forEach(cb);
} catch (e) {
  if (e instanceof TypeError && /this is null or not defined/.test(e.message)) { items = []; }
  else throw e;
}

When it happens

Trigger: Calling `[].forEach` (the polyfilled version) with a null/undefined receiver, e.g. `null.forEach(fn)`, `someVar.forEach(fn)` where someVar is undefined, or calling forEach detached without a receiver in old engines lacking native forEach.

Common situations: Old browsers (IE8 and earlier) that lack native forEach, combined with code that assumes an array exists (null API response, failed DOM selector, uninitialized variable).

Related errors

• " + g + " is not a function
• This is abstract class

AI-assisted analysis of ssssssss-team/spider-flow@c799cca99c (2026-09-08). Data as JSON: /api/errors/85a8bb0b7724d7f5. Report an issue: GitHub.

Appendix: source

Thrown at spider-flow-web/src/main/resources/static/js/layui/extends/formSelects-v4.js:206

				var b,
				    a,
				    c,
				    e = Object(this),
				    f = e.length >>> 0;if (h) {
					b = h;
				}a = new Array(f);c = 0;while (c < f) {
					var d, g;if (c in e) {
						d = e[c];g = i.call(b, d, c, e);a[c] = g;
					}c++;
				}return a;
			};
		};

		//拓展Array foreach方法
		if (!Array.prototype.forEach) {
			Array.prototype.forEach = function forEach(g, b) {
				var d, c;if (this == null) {
					throw new TypeError("this is null or not defined");
				}var f = Object(this);var a = f.length >>> 0;if (typeof g !== "function") {
					throw new TypeError(g + " is not a function");
				}if (arguments.length > 1) {
					d = b;
				}c = 0;while (c < a) {
					var e;if (c in f) {
						e = f[c];g.call(d, e, c, f);
					}c++;
				}
			};
		};

		//拓展Array filter方法
		if (!Array.prototype.filter) {
			Array.prototype.filter = function (b) {
				if (this === void 0 || this === null) {
					throw new TypeError();
				}var f = Object(this);var a = f.length >>> 0;if (typeof b !== "function") {

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