ReferenceError Invalid left-hand side in assignment

Question

my code for a rock paper scissors game  called toss  is as follows   var toss   function  one two        if one    rock   amp  amp  two    rock             console log  Tie  Try again                  more similar conditions with  else if       When I enter in the parameters  toss  rock   rock     I get this error code        ReferenceError  Invalid left-hand side in assignment    How to fix it  What this error means and what other cases when this error can happen

User · Accepted Answer

You have to use    to compare  or even      if you want to compare types   A single   is for assignment   if  one     rock   amp  amp  two     rock         console log  Tie  Try again

User · Answer

The same happened for me with eslint module  EsLinter throw Parsing error  Invalid left-hand side in assignment expression for await in second if statement   if  condition one      let result   await myFunction      if  condition two      let result   await myFunction      eslint parsing error     As strange as it sounds what fixed this error was to add   semicolon at the end of line where await occurred   if  condition one      let result   await myFunction       if  condition two      let result   await myFunction

User · Answer

Common reasons for the error     use of assignment     instead of equality          assigning to result of function foo     42 instead of passing arguments  foo 42    simply missing member names  i e  assuming some default selection    getFoo     42 instead of getFoo   theAnswer   42 or array indexing getArray     42 instead of getArray   0   42   In this particular case you want to use     or better     - What exactly is Type Coercion in Javascript   to check for equality  like if one      rock   amp  amp  two      rock    but it the actual reason you are getting the error is trickier   The reason for the error is Operator precedence  In particular we are looking for  amp  amp   precedence 6  and    precedence 3    Let s put braces in the expression according to priority -  amp  amp  is higher than   so it is executed first similar how one would do 3 4 5 6 as 3  4 5  6    if one    rock   amp  amp  two     rock         Now we have expression similar to multiple assignments like a   b   42 which due to right-to-left associativity executed as a    b   42   So adding more braces    if one       rock   amp  amp  two     rock             Finally we arrived to actual problem    rock   amp  amp  two  can t be evaluated to l-value that can be assigned to  in this particular case it will be value of two as truthy    Note that if you d use braces to match perceived priority surrounding each  equality  with braces you get no errors  Obviously that also producing different result than you d expect - changes value of both variables and than do  amp  amp  on two strings  rock   amp  amp   rock  resulting in  rock   which in turn is truthy  all the time due to behavior of logial  amp  amp    if  one    rock    amp  amp   two    rock            always executed  both one and two are set to  rock               For even more details on the error and other cases when it can happen - see specification   Assignment      LeftHandSideExpression   AssignmentExpression           Throw a SyntaxError exception if the following conditions are all true           IsStrictReference lref  is true   Left-Hand-Side Expressions  and The Reference Specification Type explaining IsStrictReference          function calls are permitted to return references  This possibility is admitted purely for the sake of host objects  No built-in ECMAScript function defined by this specification returns a reference and there is no provision for a user-defined function to return a reference

[javascript] ReferenceError: Invalid left-hand side in assignment

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