UglifyJS version 3.4.2 changes behavior of code.

[Stadly]

Bug report

Uglify version 3.4.9

See this CodePen. It shows how Parsley.js v2.8.1 changes behavior when uglified by recent versions of uglifyjs.

<input type="date" min="2000-01-02" max="2179-06-06" value="2018-11-23"> is invalidated when Parsley.js is uglified by uglifyjs version 3.4.2, but not when uglified by uglifyjs version 3.4.1.

When comparing the uglified files, these are the lines that are different:

Uglified by uglifyjs version 3.4.1

           if (this.validateDate && instance._isDateInput()) return arguments[0] = Utils.parse.date(value),
           null !== value && this.validateDate.apply(this, arguments);
           if (this.validateNumber) return !isNaN(value) && (arguments[0] = parseFloat(value),
           this.validateNumber.apply(this, arguments));

Uglified by uglifyjs version 3.4.2

            if (this.validateDate && instance._isDateInput()) return null !== (value = Utils.parse.date(value)) && this.validateDate.apply(this, arguments);
            if (this.validateNumber) return !isNaN(value) && (value = parseFloat(value), this.validateNumber.apply(this, arguments));

[kzc]

Minified code is not useful for the purposes of a bug report. There's a reason for the issue template. A complete unminified JS input exhibiting the problem is required.

Try disabling the compress option arguments and report your findings.

[Stadly]

Sorry about not including the input code. Here it comes:

Unminified

function validate(value) {
   if (this.validateDate && instance._isDateInput()) {
      arguments[0] = Utils.parse.date(arguments[0]);
      if (arguments[0] === null) return false;
      return this.validateDate.apply(this, arguments);
   }
   throw 'Validator `' + this.name + '` only handles multiple values';
}

UglifyJS 3.4.1 uglifyjs -c -b

function validate(value) {
    if (this.validateDate && instance._isDateInput()) return arguments[0] = Utils.parse.date(value), 
    null !== value && this.validateDate.apply(this, arguments);
    throw "Validator `" + this.name + "` only handles multiple values";
}

UglifyJS 3.4.2 uglifyjs -c -b

function validate(value) {
    if (this.validateDate && instance._isDateInput()) return null !== (value = Utils.parse.date(value)) && this.validateDate.apply(this, arguments);
    throw "Validator `" + this.name + "` only handles multiple values";
}

UglifyJS 3.4.1 uglifyjs -b

function validate(value) {
    if (this.validateDate && instance._isDateInput()) {
        arguments[0] = Utils.parse.date(arguments[0]);
        if (arguments[0] === null) return false;
        return this.validateDate.apply(this, arguments);
    }
    throw "Validator `" + this.name + "` only handles multiple values";
}

UglifyJS 3.4.2 uglifyjs -b

function validate(value) {
    if (this.validateDate && instance._isDateInput()) {
        arguments[0] = Utils.parse.date(arguments[0]);
        if (arguments[0] === null) return false;
        return this.validateDate.apply(this, arguments);
    }
    throw "Validator `" + this.name + "` only handles multiple values";
}

As you can see, the issue only happens with the -c flag.

[kzc]

Like I said, use -c arguments=false. Or switch to terser.

[Stadly]

Sorry, here it is:

UglifyJS 3.4.1 uglifyjs -c arguments=false -b

function validate(value) {
    if (this.validateDate && instance._isDateInput()) return arguments[0] = Utils.parse.date(arguments[0]), 
    null !== arguments[0] && this.validateDate.apply(this, arguments);
    throw "Validator `" + this.name + "` only handles multiple values";
}

UglifyJS 3.4.2 uglifyjs -c arguments=false -b

function validate(value) {
    if (this.validateDate && instance._isDateInput()) return arguments[0] = Utils.parse.date(arguments[0]), 
    null !== arguments[0] && this.validateDate.apply(this, arguments);
    throw "Validator `" + this.name + "` only handles multiple values";
}

UglifyJS 3.4.1 uglifyjs -c arguments=false

function validate(value){if(this.validateDate&&instance._isDateInput())return arguments[0]=Utils.parse.date(arguments[0]),null!==arguments[0]&&this.validateDate.apply(this,arguments);throw"Validator `"+this.name+"` only handles multiple values"}

UglifyJS 3.4.2 uglifyjs -c arguments=false

function validate(value){if(this.validateDate&&instance._isDateInput())return arguments[0]=Utils.parse.date(arguments[0]),null!==arguments[0]&&this.validateDate.apply(this,arguments);throw"Validator `"+this.name+"` only handles multiple values"}

As you can see, the issue doesn't happen with the -c arguments=false flag.

[Stadly]

@kzc Is this behavior expected?

[kzc]

I didn't look at your example in detail. If the minified code produces the wrong result then it's probably a bug. I don't know whether uglify-js is maintained at this point. There are workarounds in any case.

[alexlamsl]

Fixed by #3330