diff --git a/javascript/ql/src/Expressions/HeterogeneousComparison.ql b/javascript/ql/src/Expressions/HeterogeneousComparison.ql
index f29ea9d3896..9a84d92e8ce 100644
--- a/javascript/ql/src/Expressions/HeterogeneousComparison.ql
+++ b/javascript/ql/src/Expressions/HeterogeneousComparison.ql
@@ -170,6 +170,28 @@ string getTypeDescription(string message1, string message2, int complexity1, int
     result = message1
 }
 
+/**
+ * Holds if `e` directly uses a parameter's initial value as passed in from the caller.
+ */
+predicate isInitialParameterUse(Expr e) {
+  exists (SimpleParameter p, SsaExplicitDefinition ssa |
+    ssa.getAContributingVarDef() = p and
+    ssa.getVariable().getAUse() = e and
+    not p.isRestParameter()
+  )
+}
+
+/**
+ * Holds if `e` is an expression that should not be considered in a heterogeneous comparison.
+ *
+ * We currently whitelist these kinds of expressions:
+ *
+ *   - parameters, as passed in from the caller
+ */
+predicate whitelist(Expr e) {
+  isInitialParameterUse(e)
+}
+
 from ASTNode cmp,
      DataFlow::AnalyzedNode left, DataFlow::AnalyzedNode right,
      string leftTypes, string rightTypes,
@@ -177,6 +199,8 @@ from ASTNode cmp,
      int leftTypeCount, int rightTypeCount ,
      string leftTypeDescription, string rightTypeDescription
 where isHeterogeneousComparison(cmp, left, right, leftTypes, rightTypes) and
+      not whitelist(left.asExpr()) and
+      not whitelist(right.asExpr()) and
       leftExprDescription = capitalize(getDescription(left.asExpr(), "this expression")) and
       rightExprDescription = getDescription(right.asExpr(), "an expression") and
       leftTypeCount = strictcount(left.getAType()) and
diff --git a/javascript/ql/src/Statements/UselessConditional.ql b/javascript/ql/src/Statements/UselessConditional.ql
index 41389a75c0a..40f4dcf34b7 100644
--- a/javascript/ql/src/Statements/UselessConditional.ql
+++ b/javascript/ql/src/Statements/UselessConditional.ql
@@ -14,6 +14,7 @@
 
 import javascript
 import semmle.javascript.RestrictedLocations
+import semmle.javascript.dataflow.Refinements
 
 /**
  * Holds if `va` is a defensive truthiness check that may be worth keeping, even if it
@@ -62,19 +63,52 @@ predicate isConstant(Expr e) {
   isSymbolicConstant(e.(VarAccess).getVariable())
 }
 
+/**
+ * Holds if `e` directly uses a parameter's initial value as passed in from the caller.
+ */
+predicate isInitialParameterUse(Expr e) {
+  exists (SimpleParameter p, SsaExplicitDefinition ssa |
+    ssa.getAContributingVarDef() = p and
+    ssa.getVariable().getAUse() = e and
+    not p.isRestParameter()
+  )
+  or
+  isInitialParameterUse(e.(LogNotExpr).getOperand())
+}
+
+/**
+ * Holds if `e` directly uses the returned value from a function call that returns a constant boolean value.
+ */
+predicate isConstantBooleanReturnValue(Expr e) {
+  exists (DataFlow::CallNode call |
+    exists (call.analyze().getTheBooleanValue()) |
+    e = call.asExpr() or
+    exists (SsaExplicitDefinition ssa |
+      ssa.getDef().getSource() = call.asExpr() and
+      ssa.getVariable().getAUse() = e
+    )
+  )
+  or
+  isConstantBooleanReturnValue(e.(LogNotExpr).getOperand())
+}
+
 /**
  * Holds if `e` is an expression that should not be flagged as a useless condition.
  *
- * We currently whitelist three kinds of expressions:
+ * We currently whitelist these kinds of expressions:
  *
  *   - constants (including references to literal constants);
  *   - negations of constants;
- *   - defensive checks.
+ *   - defensive checks;
+ *   - parameters, as passed in from the caller;
+ *   - constant boolean returned values
  */
 predicate whitelist(Expr e) {
   isConstant(e) or
   isConstant(e.(LogNotExpr).getOperand()) or
-  isDefensiveInit(e)
+  isDefensiveInit(e) or
+  isInitialParameterUse(e) or
+  isConstantBooleanReturnValue(e)
 }
 
 /**
@@ -107,4 +141,4 @@ where isConditional(cond, op.asExpr()) and
           msg = "This expression always evaluates to " + cv + "."
       )
 
-select sel, msg
\ No newline at end of file
+select sel, msg
diff --git a/javascript/ql/test/library-tests/DataFlow/incomplete.expected b/javascript/ql/test/library-tests/DataFlow/incomplete.expected
index fd7bf9aeade..7345402845f 100644
--- a/javascript/ql/test/library-tests/DataFlow/incomplete.expected
+++ b/javascript/ql/test/library-tests/DataFlow/incomplete.expected
@@ -26,7 +26,6 @@
 | tst.js:65:3:65:10 | yield 42 | yield |
 | tst.js:66:13:66:25 | function.sent | yield |
 | tst.js:68:12:68:14 | h() | call |
-| tst.js:69:1:69:9 | iter.next | call |
 | tst.js:69:1:69:9 | iter.next | heap |
 | tst.js:69:1:69:13 | iter.next(23) | call |
 | tst.js:72:3:72:11 | await p() | await |
diff --git a/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/middleware-attacher-getter.js b/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/middleware-attacher-getter.js
index 6001b1bf52b..402113ab534 100644
--- a/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/middleware-attacher-getter.js
+++ b/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/middleware-attacher-getter.js
@@ -7,7 +7,7 @@ function getAttacher1 (app) {
 
 var app = express();
 getAttacher1(app);
-
+confuse(getAttacher2); // disable the type inference
 
 function getAttacher2 (app) {
     return function(h) {
@@ -17,3 +17,4 @@ function getAttacher2 (app) {
 
 var app = express();
 getAttacher2(app)(function(req, res){});
+confuse(getAttacher2); // disable the type inference
diff --git a/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/route-objects.js b/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/route-objects.js
index 43c67fdaeb4..64dbe455560 100644
--- a/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/route-objects.js
+++ b/javascript/ql/test/library-tests/frameworks/HTTP-heuristics/src/route-objects.js
@@ -58,3 +58,4 @@ function wrap(f){
     }
 }
 app[route3.method](route3.url, wrap(route3.handler));
+confuse(wrap); // confuse the type inference
diff --git a/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/HeterogeneousComparison.expected b/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/HeterogeneousComparison.expected
index 5170ec43a93..c04f07c6f44 100644
--- a/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/HeterogeneousComparison.expected
+++ b/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/HeterogeneousComparison.expected
@@ -46,3 +46,5 @@
 | tst.js:208:5:208:6 | t5 | Variable 't5' cannot be of type function or regular expression, but it is compared to $@ of type function or regular expression. | tst.js:208:12:208:13 | t2 | variable 't2' |
 | tst.js:209:5:209:6 | t3 | Variable 't3' is of type function, object or regular expression, but it is compared to $@ of type boolean, null, number, string or undefined. | tst.js:209:12:209:13 | t5 | variable 't5' |
 | tst.js:210:5:210:6 | t5 | Variable 't5' is of type boolean, null, number, string or undefined, but it is compared to $@ of type function, object or regular expression. | tst.js:210:12:210:13 | t3 | variable 't3' |
+| tst.js:225:13:225:14 | xy | Variable 'xy' is of type undefined, but it is compared to $@ of type string. | tst.js:225:20:225:24 | "foo" | an expression |
+| tst.js:233:5:233:5 | x | Variable 'x' is of type object, but it is compared to $@ of type number. | tst.js:233:11:233:12 | 42 | an expression |
diff --git a/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/tst.js b/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/tst.js
index 7de04e29c61..46199104674 100644
--- a/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/tst.js
+++ b/javascript/ql/test/query-tests/Expressions/HeterogeneousComparison/tst.js
@@ -212,4 +212,25 @@ function l() {
 
 1n == 1; // OK
 
+(function tooGeneralLocalFunctions(){
+    function f1(x) {
+        if (x === "foo") { // OK, whitelisted
+
+        }
+    }
+    f1(undefined);
+
+    function f2(x, y) {
+        var xy = o.q? x: y;
+        if (xy === "foo") { // NOT OK (not whitelisted like above)
+
+        }
+    }
+    f2(undefined, undefined);
+})();
+
+function f(...x) {
+    x === 42
+};
+
 // semmle-extractor-options: --experimental
diff --git a/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.expected b/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.expected
index a1f2aae962d..2488d37de71 100644
--- a/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.expected
+++ b/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.expected
@@ -10,3 +10,12 @@
 | UselessConditional.js:29:8:29:8 | x | Variable 'x' always evaluates to true here. |
 | UselessConditional.js:30:8:30:14 | new X() | This expression always evaluates to true. |
 | UselessConditional.js:33:7:33:7 | x | Variable 'x' always evaluates to false here. |
+| UselessConditional.js:54:9:54:13 | known | Variable 'known' always evaluates to false here. |
+| UselessConditional.js:60:9:60:15 | unknown | Variable 'unknown' always evaluates to false here. |
+| UselessConditional.js:65:5:65:5 | x | Variable 'x' always evaluates to true here. |
+| UselessConditional.js:76:13:76:13 | x | Variable 'x' always evaluates to true here. |
+| UselessConditional.js:82:13:82:13 | x | Variable 'x' always evaluates to true here. |
+| UselessConditionalGood.js:58:12:58:13 | x2 | Variable 'x2' always evaluates to false here. |
+| UselessConditionalGood.js:69:12:69:13 | xy | Variable 'xy' always evaluates to false here. |
+| UselessConditionalGood.js:85:12:85:13 | xy | Variable 'xy' always evaluates to false here. |
+| UselessConditionalGood.js:97:12:97:13 | xy | Variable 'xy' always evaluates to false here. |
diff --git a/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.js b/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.js
index 7586ed6af38..5beff0e17a0 100644
--- a/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.js
+++ b/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditional.js
@@ -44,4 +44,44 @@ async function awaitFlow(){
     }
 }
 
+(function(){
+    function knownF() {
+        return false;
+    }
+    var known = knownF();
+    if (known)
+        return;
+    if (known)
+        return;
+
+    var unknown = unknownF();
+    if (unknown)
+        return;
+    if (unknown) // NOT OK
+        return;
+});
+
+(function (...x) {
+    x || y // NOT OK
+});
+
+(function() {
+    function f1(x) {
+        x || y // NOT OK, but whitelisted
+    }
+    f1(true);
+
+    function f2(x) {
+        while (true)
+            x || y // NOT OK
+    }
+    f2(true);
+
+    function f3(x) {
+        (function(){
+            x || y // NOT OK
+        });
+    }
+    f3(true);
+});
 // semmle-extractor-options: --experimental
diff --git a/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditionalGood.js b/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditionalGood.js
index 667a1eca83f..0a1c5888e09 100644
--- a/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditionalGood.js
+++ b/javascript/ql/test/query-tests/Statements/UselessConditional/UselessConditionalGood.js
@@ -5,4 +5,97 @@ function getLastLine(input) {
   if (!lines.length)
     throw new Error("No lines!");
   return lines[lines.length-1];
-}
\ No newline at end of file
+}
+
+(function tooSpecificFunctions(){
+    function f1() {
+        return false
+    }
+    if(f1()){} // OK, whitelisted
+
+    function f2() {
+        return false
+    }
+    if(!f2()){} // OK, whitelisted
+
+    function f3() {
+        return false
+    }
+    if(!!f3()){} // OK, whitelisted
+
+    function f4() {
+        return false
+    }
+    if(f4() || o.p){} // OK, whitelisted
+
+    function f5() {
+        return false
+    }
+    var v5 = f5();
+    if(v5){} // OK, whitelisted
+
+    function f6() {
+        return false
+    }
+    var v6 = f6();
+    if(!!v6){} // OK, whitelisted
+})();
+
+(function tooGeneralFunctions(){
+    function f1(x) {
+        if(x){} // OK, whitelisted
+    }
+    f1(undefined);
+    f1({});
+
+    function f2(x) {
+        if(x){} // OK, whitelisted
+    }
+    f2(undefined);
+
+    function f3(x1) {
+        var x2 = x1;
+        if(x2){} // NOT OK, not whitelisted
+    }
+    f3(undefined);
+
+    function f4(x) {
+        if(x && o.p){} // OK, whitelisted
+    }
+    f4(undefined);
+
+    function f5(x, y) {
+        var xy = o.q? x: y;
+        if(xy && o.p){} // NOT OK, not whitelisted
+    }
+    f5(undefined, undefined);
+
+    function f6(x) {
+        if(!x){} // OK, whitelisted
+    }
+    f6(true);
+
+    function f7(x) {
+        if(!!x){} // OK, whitelisted
+    }
+    f7(true);
+
+    function f8(x, y) {
+        var xy = x || y;
+        if(xy){} // NOT OK, not whitelisted
+    }
+    f8(undefined, undefined);
+
+    function f9(x, y) {
+        var xy = !x || y;
+        if(xy){} // OK, whitelisted
+    }
+    f9(undefined, undefined);
+
+    function f10(x, y) {
+        var xy = !!x || y;
+        if(xy){} // NOT OK, not whitelisted
+    }
+    f10(undefined, undefined);
+
+})();