WebStorm 2016.2 Help

Evaluating Expressions

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Basics

WebStorm enables you to evaluate arbitrary single-line expressions and provides a way to quickly evaluate an expression in the editor at caret or a selection.

Limitations

While using the Expression Evaluation feature, be aware of the following:

  • A method can be invoked within the Expression Evaluation dialog only if the debugger has stopped at a breakpoint, but has not been paused.
  • Expression Evaluation can only be "single-level". In other words, if WebStorm stops at a breakpoint within a method called from the Expression Evaluation, you cannot use the Expression Evaluation feature again.

Evaluating arbitrary expressions

  1. Open the Evaluate Expression dialog box in one of the following ways:
    • Choose Run | Evaluate Expression on the main menu.
    • PressAlt+F8.
    • To evaluate a specific variable, select it on the Variables pane of the Debug tool window, then choose Run | Evaluate Expression or press Alt+F8.
  2. In the Evaluate Expression dialog box, specify the expression you want to evaluate. Do one of the following:
    • In the Expression field, type the expression in question or choose one of the previously evaluated expressions from the drop-down list.

      If you have selected a specific variable on the Variables pane, this variable will be displayed in the Expression text box.

    • To evaluate a code fragment, click the Code Fragment Mode button and fill in the Code Fragment text box.

      To return to the original mode, click the Expression mode button.

  3. Click the Evaluate button. The Result read-only field shows the evaluation output. If the specified expression cannot be evaluated, the Result field explains the reason.

Evaluating expressions in the editor

During a debugger session, the value of any expression is shown in the tooltip every time you hover your mouse pointer over it. If an expression contains children, clicking add expands the node and displays all children.

You can also use the Quick Evaluate expression functionality that lets you view the value of an expression using the keyboard only.

There are two ways to evaluate an expression quickly:

  1. By using the Show value tooltip on code selection functionality:
    • In the Debugger | Data Views settings page, enable the Show value tooltip on code selection option.
    • Select a code fragment with the mouse, or by clicking Ctrl+W. A tooltip with the expression value automatically appears under the selection and changes each time you change the selection:
      evaluate_selection
  2. By manually invoking the tooltip with the expression value:
    • Place the caret at the desired location, or select an expression to be evaluated.
    • Choose Run | Quick Evaluate Expression on the main menu, or press Ctrl+Alt+F8. The tooltip with the expression value appears under the selected expression.

Evaluating variables in the console pane

In the PHP and JavaScript context, you can view the values of variables right in the Debug tool window during a debugging session. This can be done in several ways:

  • Select the variable in question in the Variables pane and choose Evaluate in Console on the context menu of the selection. When you switch to the Console pane, the variable name is shown in green at > and its value is displayed below in blue.
  • Alternatively you can type the name of any variable at > in the Console manually and press Enter to have its value displayed. Code completion is at your disposal: as you type the name of a variable, WebStorm displays a suggestion list. Note that this functionality is available only when the Use Console Input toggle button is pressed.
  • To evaluate a previously evaluated variable without searching for it in the Variables pane, find the variable in question using the Up and Down arrows on you keyboard and press Enter.

See Also

Last modified: 2 September 2016