javascript nan error

I believe many beginner JavaScript will have this idea: why JavaScript is null and undefined, relative to C, C + +, Java, they are all just null, why JavaScript is differentOne, historical reasons The web search learned that,when JavaScript was born in 1995, initially, like Java, only null was set as the value represen

a negative number overflows, JavaScript returns a special value "negative zero ". This value (negative zero) is almost the same as normal zero. Javascript programmers seldom use negative zero. Division by zero does not return an error in javascript: it simply returns infinity or negative infinity (-infinity ). However

= undefined;Null,undefinedfunction Btnclick () {if (tmp = = undefined) {alert ("TMP is undefined!"); }}Analysis: If you use tmp==undefined, the value of TMP will be determined to be true regardless of whether it is null or undefined.2.2. Determine if NULLthe right approach :var tmp = NULL; Null,nan,undefinedfunction Btnclick () {if (!tmp typeof (TMP)! = "undefined" !isnan (tmp)) {ALert ("TMP is null!"); }}Orvar tmp = NULL; Null,

This article mainly introduces how to use the NaN value in JavaScript, which is the basic knowledge in JS learning, A friend may refer to the literal constant NaN without quotation marks as a special value, indicating that it is not a non-number. Since NaN is always a case of unequal comparison, taking any number, incl

This article mainly introduces how to use the NaN value in JavaScript, which is the basic knowledge in JS learning, A friend may refer to the literal constant NaN without quotation marks as a special value, indicating that it is not a non-number. Since NaN is always a case of unequal comparison, taking any number, incl

: Unknown variable name or unassigned variable.Null: Special objectNan: Special Number 1:Alert (Typeof(Undefined ));// Display 'undefined' 2:Alert (Typeof(Null));// Display 'object' 3:Alert (Typeof(""));// Display 'string' 4:Alert (Typeof(0 ));// Display 'number' 5:Alert (Typeof(False));// Display 'boolean' 6: 7: VaRA7 = Nan; 8: VaRA8 = undefined; 9: 10:Alert (TypeofA7 );// Display "Number" 11:Alert (TypeofA8); // display"Undefin

)); //Show ' object ' 3: alert (typeof(")"); //Display ' string ' 4: alert (typeof(0)); //Show ' number ' 5: alert (typeof(false)); //Show ' Boolean ' 6: 7: var a7 = NaN; 8: var a8 = undefined; 9: : alert (typeof//display "number" One : alert (typeof A8); Show "Undefined"The above indicates that Nan is a special number, and null and undefined are not equal.The function parameter is not and is empty judgment

This article mainly introduces the use of Nan value in JavaScript, is the basic knowledge of JS introductory learning, the need for friends can refer to the literal constant without quotes Nan is a special value that represents not a non-numeric number. Because Nan is always in a relatively unequal situation, in any n

caused a change in objcopy. In addition to the above 5 types, there is also a "function"type. [JavaScript] View plaincopyUndefined andNULL, the difference between NaN is described above, it is easy to distinguish undefined from the other two. Undefined determines the type of the variable, while the other two judgments are the value of the variable. Undefined can be used to indicate the following conditions

The following is transferred from: http://blog.csdn.net/hongweigg/article/details/380900931. Question: In JavaScript, typeof (undefined) = = undefined established?Answer: Not true, the global function typeof () returns a value type of string type , six possible values: "Number", "string", "Boolean", "Object", "function", and "undefined".Only typeof (undefined) = = "undefined";is set up.2, typeof (null) = = ' undefined ' established?Answer: Not valid,

"NaN action is used to indicate that a value is not a number"Nan behaves strangely in JavaScript because that Nan and any value are not equal (including itself).Nan = = = Nan; FalseBecause the following code can cause some people

two determine the value of the variable. Undefined can be used to indicate the following conditions 1. represents an undeclared variable, 2. variables declared but not assigned values, 3. null is a special object that indicates no value; NaN is a special number that indicates no value; comparison operator (==or ==) use =. If the types on both sides are different, the js engine first converts them to the same type for comparison of values; Use =, then

1. Judge undefined:? 1234 vartmp = undefined; if(typeof(tmp) == "undefined"){ alert("undefined"); } Description: typeof returned a string of six possible types: "Number", "string", "Boolean", "Object", "function", "undefined"2. Determine null:? 1234 vartmp = null; if (!tmp typeof(tmp)!="undefined" tmp!=0){ alert("null"); } 3. Determine nan: (Nan