Javascript expression calculator code _ javascript tips-js tutorial

Js expression calculator Code. For more information, see. :

Code:

<Script type = "text/javascript"> // <! [CDATA [String. prototype. trim = function () {return this. replace (/^ \ s + /,''). replace (/\ s + $/, '') ;}; function calc () {var expression = document. getElementById ("txtExpression "). value; try {document. getElementById ("txtResult "). innerText = 'calculation result: '+ calcBasic (calcComplex (expression);} catch (e) {document. getElementById ("txtResult "). innerText = e. message ;}} function calcComplex (complexExpression) {Var arr = new Array (); var left = 0; var right = 0; for (var I = 0; I <complexExpression. length; I ++) {if (complexExpression. charAt (I) = '(') {arr. push (I); left ++;} if (complexExpression. charAt (I) = ') {arr. push (I); right ++ ;}} if (left! = Right) {throw new Error ('parentheses do not match! ', '2');} var brackets = complexExpression. replace (/[^ \ (| ^ \)]/g, ''); for (I = 0; I <brackets. length; I ++) {if (brackets. charAt (I) = "(" & brackets. charAt (I + 1) = ")") {var simpleExpression = complexExpression. substr (arr [I] + 1, arr [I + 1]-arr [I]-1); if (calcBasic (simpleExpression) <0) {complexExpression = complexExpression. substr (0, arr [I]) + '[' + Math. abs (calcBasic (simpleExpression )) + ''+ ComplexExpression. substr (arr [I + 1] + 1);} else {complexExpression = complexExpression. substr (0, arr [I]) + ''+ calcBasic (simpleExpression) +'' + complexExpression. substr (arr [I + 1] + 1);} complexExpression = calcComplex (complexExpression); break ;}return complexExpression;} function calcBasic (baseExpression) {if (baseExpression. charAt (0) = '-') {baseExpression = '[' + baseExpression. Substr (1);} var constants = baseExpression. trim (). replace (/[\ * | \/| \ + | \-]/g ,''). split (/\ s +/g); for (var index in constants) {// only the symbol baseExpression = baseExpression is left. replace (/\ s +/g ,''). replace (constants [index], ''); // converts the extracted constant string to a numeric var item; if (constants [index]. trim (). charAt (0) = '[') {item = parseFloat (constants [index]. trim (). replace ('[', '-');} else {item = parseFloat (constants [index]. tr Im ();} if (isNaN (item) {throw new Error ('There is an invalid symbol! ', '0');} else {constants [index] = item ;}} if (constants. length! = BaseExpression. length + 1) {throw new Error ('expression Error! ', '1');} for (var I = 0; I <baseExpression. length; I ++) {switch (baseExpression. charAt (I) {case '*': constants. splice (I, 2, constants [I] * constants [I + 1]); baseExpression = baseExpression. replace ('*', ''); I-= 1; break; case '/': if (constants [I + 1] = 0) {throw new Error ('the divisor cannot be 0! ');} Constants. splice (I, 2, constants [I]/constants [I + 1]); baseExpression = baseExpression. replace ('/', ''); I-= 1; break; default: break; }}for (var j = 0; j <baseExpression. length; j ++) {switch (baseExpression. charAt (j) {case '+': constants. splice (j, 2, constants [j] + constants [j + 1]); baseExpression = baseExpression. replace ('+', ''); j-= 1; break; case '-': constants. splice (j, 2, constants [j]-constants [j + 1]); baseExpression = baseExpression. replace ('-', ''); j-= 1; break; default: break;} return constants [0];} //]> script </p> <p style = "text-align: center;"> <textarea id = "txtExpression" style = "width: 90%; height: 200px; overflow-y: visible; "> </textarea> <p style =" width: 90%; margin: 4px auto; text-align: left; "> <input id =" btnSubit "type =" button "onclick =" calc () "value =" computing "/> </p>
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