eval

I am trying to learn JavaScript from the Rhino book. I was trying to execute the following code from the book with regards to eval() . I am using node.js (v0.10.29) to execute the examples. var geval = eval; // aliasing eval to geval var x = 'global'; // two global variables var y = 'global'; function f () { var x = 'local'; // define a local variable eval('x += "changed";'); // direct eval sets the local variable return x; } function g () { var y = 'local'; // define a local variable geval('y += "changed";'); // indirect eval sets global variable return y; } console.log(f(), x); // =>

I've noticed that Exception.pm and Error.pm don't seem to be extensively used in the Perl community. Is that due to the large footprint of eval for exception handling? Also Perl programs appear to have a much more lenient policy regarding exception handling in general. Is there a compelling reason for this? In any event what would be the best method for exception handling in Perl? Michael Carman The consensus of the Perl community seems to be that Try::Tiny is the preferred way of doing exception handling. The "lenient policy" you refer to is probably due to a combination of: Perl not being a

Many programmers say it is a bad practice to use the eval() function: When is JavaScript's eval() not evil? I'd like to take a moment to address the premise of your question - that eval() is "evil"... Is this eval() dangerous? Buggy evaled code can violate security properties just as easily as buggy source code... Why not eval() JSON? There are a number of ways that your security may be compromised... Is there ever a good reason to use eval()? Yes - when there is no other way to accomplish the given task with a reasonable level of clarity... This eliminates 99% of cases where eval is used...

python eval 用法 eval 　　功能：将字符串str当成有效的表达式来求值并返回计算结果。 　　语法： eval(source[, globals[, locals]]) -> value 　　参数： 　　　　source：一个Python表达式或函数compile()返回的代码对象 　　　　globals：可选。 变量作用域，全局命名空间，如果被提供，则必须是一个字典对象。 　　　　locals：可选。 变量作用域，局部命名空间，如果被提供，可以是任何映射对象。 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 可以把 list , tuple , dict 和string相互转化。 ################################################# 字符串转换成列表 a = "[[1,2], [3,4], [5,6], [7,8], [9,0]]" type (a) # <type 'str'> b = eval (a) print (b) # [[1, 2], [3, 4], [5, 6], [7, 8], [9, 0]] type (b) # <type 'list'> ######################

Many developers believe that JavaScript's eval() method should be avoided. This idea makes sense from a design perspective. It is often used as an ugly workaround when a simpler, better option is available. However, I do not understand the concerns about security vulnerabilities. Certainly, running eval() gives the hacker the ability to run any JavaScript code that you can run. But can't they do this anyway? In Chrome, at least, the Developer Tools allow the end-user to run their own JavaScript. How is eval() more dangerous than the Developer Tools? As B-Con mentioned, the attacker is not the

I like the flexibility of Dynamic SQL and I like the security + improved performance of Prepared Statements. So what I really want is Dynamic Prepared Statements, which is troublesome to make because bind_param and bind_result accept "fixed" number of arguments. So I made use of an eval() statement to get around this problem. But I get the feeling this is a bad idea. Here's example code of what I mean // array of WHERE conditions $param = array('customer_id'=>1, 'qty'=>'2'); $stmt = $mysqli->stmt_init(); $types = ''; $bindParam = array(); $where = ''; $count = 0; // build the dynamic sql and